Structures incorporating polymer-inorganic particle blends

ABSTRACT

Polymer-inorganic particle blends are incorporated into structures generally involving interfaces with additional materials that can be used advantageously for forming desirable devices. In some embodiments, the structures are optical structures, and the interfaces are optical interfaces. The different materials at the interface can have differences in index-of-refraction to yield desired optical properties at the interface. In some embodiments, structures are formed with periodic variations in index-of-refraction. In particular, photonic crystals can be formed. Suitable methods can be used to form the desired structures.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to copending U.S. ProvisionalPatent application Ser. No. 60/309,887 filed Aug. 03, 2001 to Kambe etal., entitled “Index-Engineering With Nano-Polymer Composites,”incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to structures formed with polymer-inorganicparticle blends, including polymer-inorganic particle composites withbonding between the particles and the polymer. The invention furtherrelates to processing approaches, such as self-assembly, for theformation of structures from polymer-inorganic particle blends. Inaddition, the invention relates to devices formed from thepolymer-inorganic particle blends, in particular optical devices, suchas photonic crystals.

BACKGROUND OF THE INVENTION

Advances in a variety of fields have created uses for many types of newmaterials. In particular, a variety of chemical powders can be used inmany different processing contexts. Inorganic powders can introducedesired functionality in various contexts. Similarly, polymers can beused to form a variety of devices in many fields. Various polymers areavailable to provide desired properties and/or functionalities for theappropriate application as well as providing versatility in processing.

Furthermore, technological advances have increased interest in improvedmaterial processing with strict tolerances on processing parameters. Asminiaturization continues even further, material parameters will need tofall within stricter tolerances. Current integrated circuit technologyalready requires tolerances on processing dimensions on a submicronscale. The consolidation or integration of mechanical, electrical andoptical components into integral devices has created further constraintson material processing. Composite materials can be used to combinedesirable properties and/or processing capabilities of differentmaterials to obtain improved materials and performances.

An explosion of communication and information technologies includinginternet based systems has motivated a world wide effort to implementoptical communication networks to take advantage of a large bandwidthavailable with optical communication systems. Optical communicationsystems incorporate optical fibers for transmission and may include, forexample, planar optical structures for manipulating optical signals in asmaller footprint. Formation of optical devices has been basedalternatively on polymers or on inorganic materials, such as silicaglasses.

SUMMARY OF THE INVENTION

In a first aspect, the invention pertains to an optical structurecomprising an interface between a first optical material and a secondoptical material each of which comprises a polymer. The first opticalmaterial comprises a polymer-inorganic particle blend, wherein the blendcomprises inorganic particles that, when isolated, are electricalinsulators or electrical conductors.

In another aspect, the invention pertains to a structure comprising aninterface between a first material and a second material each of whichcomprises a polymer. The first material comprises a polymer-inorganicparticle composite. The composite comprises inorganic particles that areelectrical semiconductors or electrical conductors, and the inorganicparticles have an average particle size of no more than about 1 micron.

In a further aspect, the invention pertains to a material comprising apolymer-inorganic particle blend. The blend comprises inorganic particlethat are electrically conducting, and the blend is transparent tovisible light at a thickness of 100 microns.

In an additional aspect, the invention pertains to a reflective displaycomprising liquid crystal dispersed within a polymer-inorganic particleblend. The polymer-inorganic particle blend is an optical material.

Furthermore, the invention pertains to an interconnected opticalstructure comprising a first optical channel, a second optical channeland an optical interconnect optically connecting the first opticalchannel and the second optical channel. The optical interconnectcomprises a polymer-inorganic particle blend.

Also, the invention pertains to a periodic structure comprisingapproximately periodic index-of-refraction variation. The structurecomprises a first polymer-inorganic particle blend and a second opticalmaterial interspersed between regions with the polymer-inorganicparticle blend. The second optical material is selected from the groupconsisting of a second polymer-inorganic particle blend, a polymer and anon-polymer inorganic material.

In other aspects, the invention pertains to a photonic crystal structurecomprising a periodic array of a polymer-inorganic particle blend thatis interspersed with an optical material.

In further embodiments, the invention pertains to an optical structurecomprising an interface between a uniform optical inorganic material andan optical polymer-inorganic particle blend. The blend comprisesinorganic particles that are electrical insulators or electricalconductors.

In addition, the invention pertains to a display device comprising alayer of an optical polymer-inorganic particle blend that forms avisible portion of the display. The blend comprises inorganic particlesthat are electrical insulators or electrical conductors.

In additional aspect, the invention pertains to an optical devicecomprising a polymer-inorganic particle blend wherein the blendcomprises inorganic particles that exhibit non-linear opticalproperties.

Furthermore, the invention pertains to a light absorbing devicecomprising a first electrode and a polymer-inorganic particle blendarranged in a periodic structure. The periodic structure absorbselectromagnetic radiation at a desired frequency.

Also, the invention pertains to an electromechanical structurecomprising a pair of electrodes and a polymer-inorganic particlecomposite. Application of a voltage to the electrodes results in adeflection of a portion of the electromechanical structure.

In other aspects, the invention pertains to a method for producing aninterface between a first material and a second material with eachmaterial comprising a polymer and with at least one of the materialscomprising a polymer-inorganic particle blend. The method comprisescoextruding a first optical material in contact with a second opticalmaterial to form an interface between the first material and the secondmaterial.

In further aspects, the invention pertains to a method for producing aninterface between a first material and a second material with eachmaterial comprising a polymer and with at least one of the materialscomprising a polymer-inorganic particle blend. The method comprisesspin-coating the first material on top of a layer of the second materialto form an interface between the first material and the second material.The first material does not dissolve the second material in the timeframe of the spin coating process.

In another aspect, the invention pertains to a method for producing aninterface between two optical materials differing in value ofindex-of-refraction between each other by at least about 0.005. Themethod comprises implementing a self-assembly process with apolymer/inorganic particle blend to form a first optical material andlocating a second optical material in contact with the blend to form theinterface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a planar interface between apolymer-inorganic particle blend and a second material.

FIG. 2 is a schematic perspective view of an interface along an edgebetween a polymer-inorganic particle blend and a second material.

FIG. 3 is a schematic perspective view of a structure with variousinterfaces between three materials.

FIG. 4 is a perspective view of a representative waveguide structure.

FIG. 5 is a top view of a planar optical structure with an opticalcoupler/splitter within the structure noted with phantom lines.

FIG. 6 is a side view of the optical structure of FIG. 5.

FIG. 7A is a sectional view of an interconnect with a step-wise changein index-of-refraction.

FIG. 7B is a sectional view of an interconnect that tappers between afirst waveguide and a second waveguide.

FIG. 8 is a sectional view of a polymer-inorganic particle blend used asan optical adhesive to connect two optical channels.

FIG. 9 is a sectional side view of an optical channel with a bend.

FIG. 10 is a sectional side view of a reflection-type, polymer-dispersedliquid crystal display device with two display elements shown with thesection taken through the center of the elements.

FIG. 11 is a sectional side view of a tunable vertical cavitysurface-emitting laser incorporating a micro-electromechanical systemwith the section taken through membrane mounting post of themicro-electromechanical system.

FIG. 12 is a top view of an arrayed waveguide grating.

FIG. 13 is a top perspective view of an optical structure with threeoptical switches formed from polymer-inorganic particle blends.

FIG. 14 is sectional side view of the optical structure of FIG. 13 withthe section taken along line 13—13.

FIG. 15 is a sectional side view of a cross-connect optical switch withthe section taken through the switch elements.

FIG. 16 is a perspective view of a structure with a periodic array ofbars of polymer-inorganic particle blends.

FIG. 17 is an optical structure with a periodic array of higherindex-of-refraction material within the optical structure.

FIG. 18 is a perspective view of an optical structure with a twodimensional array of higher index-of-refraction material, which can be aportion of a larger optical structure.

FIG. 19 is a perspective view of an optical structure with a threedimensional array of higher index-of-refraction material, which can be aportion of a larger optical structure.

FIG. 20 is a top view of an optical structure with a step-wise gradualchange in index-of-refraction to form a periodic variation inindex-of-refraction.

FIG. 21 is a plot of index-of-refraction as a function of distance forthe optical structure of FIG. 20.

FIG. 22 is a sectional side view of a tunable optical filter with thesection taken through the tuning electrodes.

FIG. 23 is a sectional side view of a laser with two Bragg gratings aspartial mirrors.

FIG. 24 is a perspective view of a laser pyrolysis apparatus used in theproduction of titanium oxide.

FIG. 25 is a cut away side view of the laser pyrolysis apparatus of FIG.24.

FIG. 26 is a sectional view of the laser pyrolysis apparatus of FIG. 24taken along line 26—26 of FIG. 24.

FIG. 27 is a plot of three x-ray diffractograms for each of threedifferent TiO₂ powder samples.

FIG. 28 is a transmission electron micrograph of representative titaniumoxide nanoparticles formed by laser pyrolysis.

FIG. 29 is a plot of an absorption spectrum in arbitrary units as afunction of wavelength for a 0.003 weight percent dispersion of TiO₂-3in ethanol.

FIG. 30 is a plot of an absorption spectrum in arbitrary units as afunction of wavelength for a 0.003 weight percent dispersion of acommercial brand of TiO₂ in ethanol.

FIG. 31 is a plot of refractive index as a function of particle loadingfor titanium oxide nanoparticles in poly acrylic acid.

DETAILED DESCRIPTION OF THE INVENTION

Versatile materials and structures can be formed from blends comprisingpolymers and inorganic particles. In particular, a polymer-inorganicparticle blend can be combined with another material, which may or maynot be another blend, to form structures with appropriate interfacesbetween the different materials. Inorganic powders and correspondingpolymer-inorganic particle blends can be used in the production ofdevices, such as flat panel displays, electronic circuits, optical andelectro-optical materials, optical devices and integrated opticalcircuits. In some embodiments, the polymers and the inorganic particlesare chemically bonded to stabilize the resulting composite. For theformation of optical materials and optical structures, thepolymer-inorganic particle blend materials have optical properties basedon the components of the optical materials. In general, by selecting thecompositions and particle loadings, the properties, such as opticalproperties, of the blend can be correspondingly selected. Desirableoptical structures may involve interfaces between thepolymer/inorganic-particle blends and another polymer material, such asanother polymer-inorganic particle blend, or a uniform inorganicmaterial, such as an optical glass. Specifically, optical structuresgenerally involve interfaces between optical materials with differingoptical properties, e.g., index-of-refraction. Various processingapproaches can be used effectively to form desired optical structures.Optical and non-optical devices can be formed advantageously thatincorporate the polymer-inorganic particle blends. Some structures ofinterest have a period variation in materials with one or more of thematerials being a polymer-inorganic particle blend.

Polymer-inorganic particle blends can be used to engineer processablematerials with wide ranges of properties, such as index-of-refraction.In addition to having versatility with respect to functional properties,polymer-inorganic particle blends can have desirable mechanicalproperties, such as durability. A range of polymers are suitable forincorporation into the composites, including both organic polymers andinorganic polymers, such as polysiloxanes. The inorganic particlesgenerally include metal or metalloid elements in their elemental form orin compounds. Specifically, the inorganic particles can include, forexample, elemental metal or elemental metalloid, i.e. unionizedelements, metal/metalloid oxides, metal/metalloid nitrides,metal/metalloid carbides, metal/metalloid sulfides, metal/metalloidsilicates, metal/metalloid phosphates or combinations thereof. As usedherein, inorganic particles include carbon particles, such asfullerenes, carbon black, graphite and combinations thereof. Inorganicparticles excluding carbon particles can be referred to as non-carboninorganic particles. Metalloids are elements that exhibit chemicalproperties intermediate between or inclusive of metals and nonmetals.Metalloid elements include silicon, boron, arsenic, antimony, andtellurium. While phosphorous is located in the periodic table near themetal elements, it is not generally considered a metalloid element.However, P₂O₅ and doped forms of P₂O₅ are good optical materials similarto some metalloid oxides, and other optical materials doped withphosphorous, e.g., in the form of P₂O₅, can have desirable opticalproperties. For convenience, as used herein including in the claims,phosphorous is also considered a metalloid element.

The inorganic particles can be incorporated at a range of loadings intothe blends. High inorganic particle loadings of up to about 50 weightpercent or greater can be achieved with well dispersed particles. Inaddition, in embodiments involving chemically bonded composites, theamount of the linker compounds bonded to the inorganic particles can beadjusted to vary the degree of crosslinking obtained with the polymer.

In some aspects of the invention, polymer inorganic-particle blendscomprise polymer-inorganic particle composites with chemical bondingbetween the inorganic particles and the polymer. In other embodiments,the blends comprise mixtures of inorganic particles and polymers. Thecomposition of the components of the blends and the relative amounts ofthe components can be selected to yield desired properties, such asoptical properties.

In embodiments of the polymer-inorganic particle blends involvingchemical bonding between the polymer and the inorganic particles, thepolymer is selected or modified to include appropriate functional groupsto chemically bond with the inorganic particles or with functionalgroups of a linker compound. A linker compound can facilitate theformation of the resulting composite. Specifically, in theseembodiments, the composites include a monomer/polymer component,inorganic particles, and linker compounds that bridge the inorganicparticles and the monomer/polymer. In the case of monomer units beingjoined to the linker compound, a polymer is formed with the formation ofthe composite. For simplicity in notation, the monomer/polymer unitjoined with the linker and assembled into the composite will be referredto generally as a polymer, although it is recognized that in some casesthe unit can be a monomer or polymer, such as a dimer, trimer or largerpolymer structures. The molecular weights of the polymers can beselected to vary the properties of the resulting composite.

In some embodiments, it may be advantageous to use collections ofinorganic particles having an average diameter of less than about 500nanometers (mn). Suitable nanoparticles can be formed, for example, byflame synthesis, combustion, or sol gel approaches. Methods forsynthesizing inorganic particles with particular high uniformity includeradiation-based pyrolysis/laser pyrolysis in which light from an intenseradiation source drives the reaction to form the particles. Forconvenience, this application refers to radiation-based pyrolysis andlaser pyrolysis interchangeably, since a suitable intense source ofelectromagnetic radiation can be used in place of a laser. Laserpyrolysis is useful in the formation of particles that are highlyuniform in composition, crystallinity and size.

The use of nanoscale particles within the polymer/inorganic particleblends can impart improved and/or desired properties for someapplications. In particular, for the formation of optical materials,nanoparticles can provide desirable optical performance due to desirableoptical properties, such as generally decreased scattering. High-qualitynanoparticles are desirable for the generation of homogeneously mixednanoparticle-polymer blends with well-defined optical properties.Specifically, it is desirable to have particles in which the primaryparticles are not agglomerated such that the primary particles can bedispersed effectively to form the composite. High-quality nanoparticlesto form nanocomposites can be produced on a commercial scale, asdescribed in U.S. Pat. No. 5,958,348 to Bi et al., entitled “EfficientProduction of Particles By Chemical Reaction,” incorporated herein byreference, and as described further below.

Since a wide range of inorganic particles and polymers can beincorporated into the composites described herein, the composites aresuitable for a wide range of applications. Specifically, the materialsand structures described herein are suitable for applications including,for example, structural applications, electronics applications andoptical applications. Optical applications are described herein in moredetail, although all applications are contemplated for the improvedstructures involving the polymer-inorganic particle blends. Onesignificant advantage from the use of polymer-inorganic particle blendsis the ability to control physical properties such as photonic orelectronic parameters over a wide range. For example, if the inorganicparticles have a high index-of-refraction, a variety of optical devicesor optical coatings can be formed over wide range and controllablevalues of index-of-refraction. High index-of-refraction materials aredesirable to control light propagation. The index-of-refraction of thecomposite can be controlled by adjusting particle loading.

The ability to control index-of-refraction has been demonstrated throughthe study of the photonic/optical properties of nanoparticle-polymercomposites. For example, the refractive index, which determines thepropagation of light within a material or device structure, can bestudied as a function of parameters of the blend. Optical observationsfrom polymer-inorganic nanoparticle composites are presented in theexamples below. In particular, structural and optical properties ofindividual nano-TiO₂ particles are also described to show correlationsbetween properties of nanoparticles and subsequent nanocomposites. Theoptical measurements with nano-TiO₂-based polymer composites confirm theability to obtain high refractive index polymer-inorganic particleblends.

Controlled management of the refractive index (n) is important forphotonic device applications. Index engineering as described hereinincludes formation of materials with desired refractive indices andtheir contrast with indices of adjacent materials at interfaces in anoptical structure. Modulation of the refractive index by external fieldsmay be achieved also.

Generally, the polymer-inorganic particle blends provide both forconsiderable versatility with respect to composition and correspondingproperties as well as processing versatility for the formation ofstructures ranging from the straightforward to the complex. For opticalapplications, index-of-refraction can be selected through thecorresponding selection of components of the blend and the particleloading. Conventional silica glass exhibits n˜1.45, depending on thedopant and the level of doping. At the other end of the range, compoundsemiconductors such as InP have n˜3.4. There is a large gap in betweenthe two regions, which has not been covered adequately by existingmaterials systems. Even if the gap is covered by multiple materials,there is a significant challenge to form a workable interface betweenthem. In contrast, polymer-inorganic particle blends formed withinorganic particles, such as nanoparticles, and a polymer matrix providethe ability to select a particular desired value of index-of-refraction.It has been found that once the high-index particles, in particularnanoparticles, and a polymer host material are chosen, the loading levelof the nanoparticles directly determines the index of the entirecomposite.

By combining a plurality of materials of which one or more is apolymer-inorganic particle blend, interfaces can be formed betweenmaterials within structures such that the overall properties and/orfunctionality have desired features. For optical applications, theoptical interface can involve optical materials with a selecteddifference in indices-of-refraction between the different materials. Thepolymer-inorganic particle blends can be used to engineer theindex-of-refraction, which can be used to reduce the size of opticalcomponents. In particular, high index contrast at optical interfaces canbe used to reduce device size, i.e., miniaturization.

In addition, the polymer-inorganic particle blends can be formed intoheterostructures designed for particular applications. For some opticalapplications, the polymer-inorganic particle blends can be formed intoperiodic structures. The formation of periodic structures can beparticularly advantageous in optical structures for the formation of,for example, structures with periodically modulated index-of-refraction.Optical materials with period variation in index-of-refraction can beused to form gratings or photonic crystals. The periodicity can extendin one, two or three dimensions.

Using polymer-inorganic particle blends, high index blends can be formedin association with low index materials, such as polymers with noparticle loadings. With these associated materials, interfaces can beformed with large changes in index-of-refraction between the twomaterials at the interface. This large change in index-of-refraction canbe used advantageously for the reflection of light and/or theconfinement of light within a material. In particular, these large indexchanges can be used advantageously in the formation of displays andother optical devices.

In particular, the use of polymer/inorganic particle composites isparticularly appropriate for the formation of devices with a selecteddielectric constant/index-of-refraction. Through index-of-refractionengineering, the materials can be designed specifically for a particularapplication through corresponding selection of the index-of-refraction.Appropriate selection of index-of-refraction can be important for thepreparation of either electrical or optical materials. Theindex-of-refraction is approximately the square root of the dielectricconstant when there is no optical loss, so that the engineering of theindex-of-refraction corresponds to the engineering of the dielectricconstant. Thus, the index-of-refraction/dielectric constant is relatedto both the optical and electrical response of a particular material.Index-of-refraction engineering can be especially advantageous in thedesign of optical or electrical interconnects. The processing approachesdescribed herein, including for example the self-assembly approaches,can be used to control domain size of materials forming devices and/orperiodicity of the material compositions/index-of-refraction. Structurediameters and periodicities can be obtained on a submicron scale.Desirable size and/or periodicity length scales generally depend on thewavelengths of light. In addition, small size/periodicity scales can beused if index-of-refraction values change by larger amounts atinterfaces. The use of nanoparticles and/or the ability to formsubmicron scale structures provides the ability to form quantum effectdevices.

The polymer-inorganic particle blends can be processed using manystandard polymer-processing approaches. Particularly suitable approachesgenerally depend on the specific structure being formed. However, in theformation of interfaces between the polymer-inorganic particle blendsand other materials, certain approaches can be particularly suitable.For example, uniform layers can be applied by spin coating a solvatedblend onto a substrate, such as a silicon wafer. The layers can bestacked by spin coating the materials sequentially. The solvents can beselected such that solvent used during the application of one layer doesnot dissolve a previously applied layer. In addition, extrusion of asolvated blend or a melt can be used to form interfaces. The multiplelayers may or may not be coextruded. Calendering can be used to improvethe qualities of the interface. Other molding and coating approaches canalso be used. In general, the processing of the polymer-inorganicparticle blends may or may not involve a substrate.

In addition, polymer-inorganic particle blends can be processed usingself-assembly techniques to form periodic structures. In particular, forsome optical applications, self-assembly techniques can be used to formperiodic optical structures with periodic interfaces between twomaterials with a difference in value of index-of-refraction between thetwo materials. Generally, the periodic structure includes apolymer-inorganic particle blend as one or both of the periodicallyvarying materials in the periodic structure in one dimension, twodimensions or three dimensions. The two dimensional variation inindex-of-refraction can be used to construct two-dimensional photoniccrystals. Similarly, a three dimensional variation inindex-of-refraction can be used to construct three-dimensional photoniccrystals. Three-dimensional photonic crystals may be used to form anideal solid state laser without natural emission due to a photonic bandgap. On the other hand, two-dimensional photonic crystals may lead tointegration of surface emitting devices and waveguides to formwavelength-division-multiplexers.

The polymer-inorganic particle blends can be advantageously incorporatedinto a variety of devices, especially optical devices. Relevant devicesinclude, for example, optical attenuator, optical splitter/coupler,optical switch, modulator, interconnect, optical isolator, opticaladd-drop multiplexer (OADM), optical amplifier, optical polarizer,optical circulator, phase shifter, optical mirror/reflector, opticalphase-retarder, optical detector, displays, micro-electromechanicalstructures (MEMS), tunable filters, optical switches, Bragg gratings,mirrors, band pass filters, arrayed waveguide gratings (AWG), lasers,photonic crystals and quasicrystals. The devices can be placed withinoptical fibers or on planar optical structures. In particular, withinplanar optical structures, the devices can be part of a planar opticalcircuit with integrated optical devices.

Polymer-Inorganic Particle Blends

The particle-inorganic particle blends involve inorganic particlesdistributed throughout a polymer matrix such that the resulting blendincorporates aspects of both the inorganic particles and the polymer.The inorganic particles may or may not be chemically bonded to thepolymer. The bonding of the inorganic particle to the polymer caninvolve a linker that is used to activate the surface of the inorganicparticles for bonding with the polymer. Suitable blends can involveeither low particle loadings or high particle loadings depending on theparticular application. Similarly, the composition of the polymercomponent and the inorganic particle components can be selected toachieve desired properties of the resulting blend. The blends,especially polymer-inorganic particle composites, may represent asynergistic effect of the combined component.

The inorganic particles can be incorporated at a range of loadings intothe composite. Composites with low particle loadings can be producedwith high uniformity. Low loadings, such as one or two percent or less,can be desirable for some applications. In addition, high inorganicparticle loadings can be achieved with well-dispersed particles. Inaddition, high inorganic particle loadings of up to about 80 weightpercent or greater can be achieved with well dispersed particles. Ingeneral, the inorganic particle loadings are from about 0.1 weightpercent to about 90 weight percent, in other embodiments from about 1weight percent to about 85 weight percent, in further embodiments fromabout 3 weight percent to about 80 weight percent, in additionalembodiments from about 5 weight percent to about 65 weight percent andin some embodiments from about 10 to about 50 weight percent. A personof skill in the art will recognize that other ranges within theseexplicit ranges are contemplated and are within the present disclosure.In addition, the amount the linker compounds bonded to the inorganicparticles can be adjusted to vary the degree of crosslinking obtainedwith the polymer.

As noted above, the polymer-inorganic particle blends can involvechemical bonding between the inorganic particles and the polymers. Forconvenience, blends having chemical bonding between at least a portionof the inorganic particles and the polymer are called polymer-inorganicparticle composites. Chemical bonding is considered to broadly coverbonding with some covalent character with or without partial ionicbonding character and can have properties of ligand-metal bonding. Inother embodiments, the inorganic particles are simply embedded withinthe polymer matrix by the physical properties of the matrix. Forconvenience, blends not involving chemical bonding between the inorganicparticles and the polymer matrix are called polymer-inorganic particlemixtures. Of course, polymer-inorganic particle mixtures generallyinvolve non-bonding electrostatic interactions, such as van der Waalsinteractions, between the polymer and the inorganic particles.

While mixtures are suitable in many contexts, the formation ofpolymer-inorganic particle composites can have advantages with respectto stability and uniformity of the blend. Specifically, high particleloadings can be achieved in a composite without agglomeration of theparticles, provided that the particles are functionalized with groupsthat do not easily bond to themselves, which can result in the formationof hard agglomerates. In addition, in relevant embodiments, the amountthe linker compounds bonded to the inorganic particles can be adjustedto vary the degree of crosslinking obtained with the polymer.

The composites with bonding between the polymer and the particlescomprise a monomer/polymer component, inorganic particles, and linkercompounds that bridge the inorganic particles and the monomer/polymer.In the case of monomer units being joined to the linker compound, apolymer is formed with the formation of the composite. For simplicity innotation, the monomer/polymer unit joined with the linker and assembledinto the composite will be referred to generally as a polymer, althoughit is recognized that in some cases the unit can be a monomer orpolymer, such as a dimer, trimer or larger polymer structures.

The linker compounds have two or more functional groups. One functionalgroup of the linker is suitable for chemical bonding to the inorganicparticles. Chemical bonding is considered to broadly cover bonding withsome covalent character with or without polar bonding and can haveproperties of ligand-metal bonding along with various degrees of ionicbonding. The functional group is selected based on the composition ofthe inorganic particle. Another functional group of the linker issuitable for covalent bonding with the polymer. Covalent bonding refersbroadly to covalent bonds with sigma bonds, pi bonds, other delocalizedcovalent bonds and/or other covalent bonding types, and may be polarizedbonds with or without ionic bonding components and the like. Convenientlinkers include functionalized organic molecules.

Various structures can be formed based on the fundamental idea offorming the chemically bonded polymer/inorganic particle composites. Thestructures obtained will generally depend on the relative amounts ofpolymer/monomers, linkers and inorganic particles as well as thesynthesis process itself. Linkers may be identified also as couplingagents or crosslinkers. Furthermore, in some embodiments,polymer-inorganic particle composites, as well as polymer-inorganicparticle blends, can comprise a plurality of different polymers and/or aplurality of different inorganic particles. Similarly, if apoly-inorganic particle blend comprises a plurality of different polymerand/or a plurality of different inorganic particles, all of the polymerand/or inorganic particles can be chemically bondinged within thecomposite or, alternatively, only a fraction of the polymers andinorganic particles can be chemically bonded within the composite. Ifonly a fraction of the polymer and/or inorganic particles are chemicallybonded, the fraction bonded can be a random portion or a specificfraction of the total polymer and/or inorganic particles.

To form the desired composites, the inorganic particles can be modifiedon their surface by chemical bonding to one or more linker molecules.The ratio of linker composition to inorganic particles can be at leastone linker molecule per inorganic particle. The linker molecules surfacemodify the inorganic particles, i.e., functionalize the inorganicparticles. While the linker molecules can bond to the inorganicparticles, they can be, but are not necessarily, bonded to the inorganicparticles prior to bonding to the polymers. They can be bonded first tothe polymers and only then bonded to the particles. Alternatively, theycan bond to the two species simultaneously.

In some embodiments, the linker is applied to form at least asignificant fraction of a monolayer on the surface of the particles. Inparticular, for example, at least about 20% of a monolayer can beapplied to the particles, and in other embodiments, at least about 40%of a monolayer can be applied. Based on the measured BET surface areasof the particles, a quantity of linker can be used corresponding up tocoverage about ½, 1 and 2 of the particle surface relative to amonolayer of the linker. A person of ordinary skill in the art willrecognize that other ranges within these explicit ranges arecontemplated and are within the present disclosure. A monolayer iscalculated based on measured surface area of the particles and anestimate of the molecular radius of the linker based on accepted valuesof the atomic radii. Excess linker reagent can be added because not allof the linker binds and some self-polymerization of the linker reagentcan take place. To calculate the coverage, the linker can be assumed tobond to the particle normal to the surface. This calculation provides anestimate of the coverage. It has been found experimentally that highercoverage could be placed over the surface of the particles thanestimated from these calculations. With these high linker coverages, thelinkers presumably form a highly crosslinked structure with thepolymers. At each inorganic particle, multi-branched crosslinkingstructures are formed.

The inorganic particles can be bonded through the linker compound intothe polymer structure, or the particles can be grafted to polymer sidegroups. The bonded inorganic particles can, in most embodiments,crosslink the polymer. Specifically, most embodiments involve starcrosslinking of a single inorganic particle with several polymer groups.The structure of the composite can generally be controlled by thedensity of linkers, the length of the linkers, the chemical reactivityof the coupling reaction, the density of the reactive groups on thepolymer as well as the loading of particles and the molecular weightrange of the polymer (i.e., monomer/polymer units). In alternativeembodiments, the polymer has functional groups that bond directly withthe inorganic particles, either at terminal sites or at side groups. Inthese alternative embodiments, the polymer includes functional groupscomparable to appropriate linker functional groups for bonding to theinorganic particles.

A range of polymers is suitable for incorporation into the composites,including, without limitation, organic polymers, inorganic polymers,such as polysiloxanes, and combinations and copolymers thereof. If thepolymers are formed prior to reacting with the functionalized inorganicparticles, the molecular weights of the polymers can be selected to varyto properties of the resulting composite. The polymer is selected orsynthesized to include appropriate functional groups to covalently bondwith functional groups of the linker compound.

The frame of the linker supporting the functional groups is generally anorganic compound, although it may also include silyl and/or siloxymoieties. The organic linker frame can comprise any reasonable organicmoiety including, for example, linear or branched carbon chains,cyclical carbon moieties, saturated carbon moieties, unsaturated carbonmoieties, aromatic carbon units, halogenated carbon groups andcombinations thereof. The structure of the linker can be selected toyield desirable properties of the composite. For example, the size ofthe linker is a control parameter that may affect the periodicity of thecomposite and the self-organization properties.

Many different types of polymers are suitable as long as they haveterminal groups and/or preferably side groups capable of bonding to alinker. Suitable organic polymers include, for example, polyamides(nylons), polyamides, polycarbonates, polyurethanes, polyacrylonitrile,polyacrylic acid, polyacrylates, polyacrylamides, polyvinyl alcohol,polyvinyl chloride, heterocyclic polymers, polyesters, modifiedpolyolefins and copolymers and mixtures thereof. Composites formed withnylon polymers, i.e., polyamides, and inorganic nanoparticles can becalled Nanonylon™. Suitable polymers include conjugated polymers withinthe polymer backbone, such as polyacetylene, and aromatic polymerswithin the polymer backbone, such as poly(p-phenylene), poly(phenylenevinylene), polyaniline, polythiophene, poly(phenylene sulfide),polypyrrole and copolymers and derivatives thereof. Some polymers can bebonded to linkers at functional side groups. The polymer can inherentlyinclude desired functional groups, can be chemically modified tointroduce desired functional groups or copolymerized with monomer unitsto introduce portions of desired functional groups. Similarly, somecomposites include only a single polymer/monomer composition bonded intothe composite. Within a crosslinked structure, a polymer is identifiableby 3 or more repeat units along a chain, except for hydrocarbon chainswhich are not considered polymers unless they have a repeating sidegroup or at least about 50 carbons—carbon bonds within the chain.

Preferred silicon-based polymers include polysilanes, polysiloxane(silicone) polymers, such as poly(dimethylsiloxane) (PDMS) andcopolymers and mixtures thereof as well as copolymers and mixtures withorganic polymers. Polysiloxanes are particularly suitable for formingcomposites with grafted inorganic particles. To form these graftedcomposites, the polysiloxanes can be modified with amino and/orcarboxylic acid groups. Polysiloxanes are desirable polymers because oftheir transparency to visible and ultraviolet light, high thermalstability, resistance to oxidative degradation and its hydrophobicity.Other inorganic polymers include, for example, phosphazene polymers(phosphonitrile polymers).

Appropriate functional groups for binding with the polymer depend on thefunctionality of the polymer. Generally, the functional groups of thepolymers and the linker can be selected appropriately based on knownbonding properties. For example, carboxylic acid groups bond covalentlyto thiols, amines (primary amines and secondary amines) and alcoholgroups. As a particular example, nylons can include unreacted carboxylicacid groups, amine groups or derivatives thereof that are suitable formcovalently bonding to linkers. In addition, for bonding to acrylicpolymers, a portion of the polymer can be formed from acrylic acid orderivatives thereof such that the carboxylic acid of the acrylic acidcan bond with amines (primary amines and secondary amines), alcohols orthiols of a linker. The functional groups of the linker can provideselective linkage either to only particles with particular compositionsand/or polymers with particular functional groups. Other suitablefunctional groups for the linker include, for example, halogens, silylgroups (—SiR_(3-x)H_(x)), isocyanate, cyanate, thiocyanate, epoxy, vinylsilyls, silyl hydrides, silyl halogens, mono-, di- andtrihaloorganosilane, phosphonates, organometalic carboxylates, vinylgroups, allyl groups and generally any unsaturated carbon groups(—R′—C═C—R″), where R′ and R″ are any groups that bond within thisstructure. Selective linkage can be useful in forming compositestructures that exhibit self-organization.

Upon reaction of the polymer functional groups with the linkerfunctional groups, the identity of initial functional groups is mergedinto a resultant or product functional group in the bonded structure. Alinkage is formed that extends from the polymer. The linkage extendingfrom the polymer can include, for example, an organic moiety, a siloxymoiety, a sulfide moiety, a sulphonate moiety, a phosphonate moiety, anamine moiety, a carbonyl moiety, a hydroxyl moiety, or a combinationthereof. The identity of the original functional groups may or may notbe apparent depending on the resulting functional group. The resultingfunctional groups generally can be, for example, an ester group, anamide group, an acid anhydride group, an ether group, a sulfide group, adisulfide group, an alkoxy group, a hydrocarbyl group, a urethane group,an amine group, an organo silane group, a hydridosilane group, a silanegroup, an oxysilane group, a phosphonate group, a sulphonate group or acombination thereof.

If a linker compound is used, one resulting functional group generallyis formed where the polymer bonds to the linker and a second resultingfunctional group is formed where the linker bonds to the inorganicparticle. At the inorganic particle, the identification of thefunctional group may depend on whether particular atoms are associatedwith the particle or with the functional group. This is just anomenclature issue, and a person of skill in the art can identify theresulting structures without concern about the particular allocation ofatoms to the functional group. For example, the bonding of a carboxylicacid with an inorganic particle may result in a group involving bondingwith a non-metal/metalloid atom of the particle; however, an oxo groupis generally present in the resulting functional group regardless of thecomposition of the particle. Ultimately, a bond extends to a metalmetalloid atom.

Appropriate functional groups for bonding to the inorganic particlesdepends on the character of the inorganic particles. U.S. Pat. No.5,494,949 to Kinkel et al., entitled “SURFACE-MODIFIED OXIDE PARTICLESAND THEIR USE AS FILLERS AND MODIFYING AGENTS IN POLYMER MATERIALS,”incorporated herein by reference, describes the use of silylating agentsfor bonding to metal/metalloid oxide particles. The particles havealkoxy modified silane for bonding to the particles. For example,preferred linkers for bonding to metal/metalloid oxide particles includeR¹R²R³—Si—R⁴, where R¹, R², R³ are alkoxy groups, which can hydrolyzeand bond with the particles, and R⁴ is a group suitable for bonding tothe polymer. Trichlorosilicate (—SiCl₃) functional groups can react withan hydroxyl group at the metal oxide particle surface by way of acondensation reaction.

Generally, thiol groups can be used to bind to metal sulfide particlesand certain metal particles, such as gold, silver, cadmium and zinc.Carboxyl groups can bind to other metal particles, such as aluminum,titanium, zirconium, lanthanum and actinium. Similarly, amines andhydroxide groups would be expected to bind with metal oxide particlesand metal nitride particles, as well as to transition metal atoms, suchas iron, cobalt, palladium and platinum.

The identity of the linker functional group that bonds with theinorganic particle may also be modified due to the character of thebonding with the inorganic particle. One or more atoms of the inorganicparticle are involved in forming the bond between the linker and theinorganic particle. It may be ambiguous if an atom in the resultinglinkage originates from the linker compound or the inorganic particle.In any case, a resulting or product functional group is formed joiningthe linker molecule and the inorganic particle. The resulting functionalgroup can be, for example, one of the functional groups described aboveresulting from the bonding of the linker to the polymer. The functionalgroup at the inorganic particle ultimately bonds to one or moremetal/metalloid atoms.

In some embodiments, the polymer incorporates the inorganic particlesinto the polymer network. This can be performed by reacting a functionalgroup of the linker compound with terminal groups of a polymer molecule.Alternatively, the inorganic particles can be present during thepolymerization process such that the functionalized inorganic particlesare directly incorporated into the polymer structure as it is formed. Inother embodiments, the inorganic particles are grafted onto the polymerby reacting the linker functional groups with functional groups onpolymer side groups. In any of these embodiments, the surfacemodified/functionalized inorganic particles can crosslink the polymer ifthere are sufficient linker molecules, i.e., enough to overcomeenergetic barriers and form at least two or more bonded links to thepolymer. Generally, an inorganic particle will have many linkersassociated with the particle. Thus, in practice, the crosslinkingdepends on the polymer-particle arrangement, statistical interaction oftwo crosslinking groups combined with molecular dynamics and chemicalkinetics.

In some embodiments, the composite is formed into localized structuresby self-assembly. The composition and/or structure of the composite canbe selected to encourage self-organization of the composite itself. Forexample, block copolymers can be used such that the different blocks ofthe polymer segregate, which is a standard property of many blockcopolymers. Suitable block copolymers include, for example,polystyrene-block-poly(methyl methacrylate),polystyrene-block-polyacrylamide, polysiloxane-block-polyacrylate andmixtures thereof. These block copolymers can be modified to includeappropriate functional groups to bond with the linkers. For example,polyacrylates can be hydrolyzed or partly hydrolyzed to form carboxylicacid groups, or acrylic acid moieties can be substituted for all or partof the acrylated during polymer formation if the acid groups do notinterfere with the polymerization. Alternatively, the ester groups inthe acrylates can be substituted with ester bonds to diols or amidebonds with diamines such that one of the functional groups remains forbonding with a linker. Block copolymers with other numbers of blocks andother types of polymer compositions can be used.

The inorganic particles can be associated with only one of the polymercompositions within the block such that the inorganic particles aresegregated together with that polymer composition within the segregationblock copolymer. For example, an AB di-block copolymer can includeinorganic particles only within block A. Segregation of the inorganicparticles can have functional advantages with respect to takingadvantage of the properties of the inorganic particles. Similarly,tethered inorganic particles may separate relative to the polymer byanalogy to different blocks of a block copolymer if the inorganicparticles and the corresponding polymers have different solvationproperties. In addition, the nanoparticles themselves can segregaterelative to the polymer to form a self-organized structure.

Other ordered copolymers include, for example, graft copolymers, combcopolymers, star-block copolymers, dendrimers, mixtures thereof and thelike. Ordered copolymers of all types can be considered a polymer blendin which the polymer constituents are chemically bonded to each other.Physical polymer blends may also be used and may also exhibitself-organization, as described in the examples below. Polymer blendsinvolve mixtures of chemically distinct polymers. The inorganicparticles may bond to only a subset of the polymer species, as describedabove for block copolymers. Physical polymer blends can exhibitself-organization similar to block copolymers. The presence of theinorganic particles can sufficiently modify the properties of thecomposite that the interaction of the polymer with inorganic particlesinteracts physically with the other polymer species differently than thenative polymer alone. In particular, the presence of nanoparticleswithin the polymer-inorganic particle blends can result in a blend thatis sensitive to weak fields due to the small particle size. Thissensitivity can be advantageously used in the formation of devices.Processes making use of small particles generally can be referred to asa soft matter approach.

Regardless of the self-organization mechanism, some self-organizedcomposites involve nanoparticles aligned with periodicity in asuperstructure or super crystal structure, i.e., a periodic array ofcrystalline particles. The particles may or may not be crystallinethemselves yet they will exhibit properties due to the ordered structureof the particles. Photonic crystals make use of these crystalsuperstructures, as described further below.

Exemplary embodiments of polymer-inorganic particle composites aredescribed further in copending and commonly assigned U.S. patentapplication Ser. No. 09/818,141, now U.S. Pat. No. 6,599,631 to Kambe etal., entitled “Polymer-Inorganic Particle Composites,” incorporatedherein by reference.

Inorganic Particles

In general, any reasonable inorganic particles can be used to form theblends. In some embodiments, the particles have an average diameter ofno more than about one micron. For some applications of interest, thecomposition of the particles is selected to impart desired properties tothe composite. Thus, in the formation of optical materials for example,the optical properties of both the polymer and the inorganic particlescan be significant. It is expected that the index-of-refraction of thecomposite material is roughly the linear combination based on the weightratios of the index-of-refractions of the inorganic particles and thepolymer to quite high particle loadings by weight.

Suitable nanoparticles can be formed, for example, by laser pyrolysis,flame synthesis, combustion, or sol gel approaches. In particular, laserpyrolysis is useful in the formation of particles that are highlyuniform in composition, crystallinity and size. Laser pyrolysis involveslight from an intense light source that drives the reaction to form theparticles. Laser pyrolysis is an excellent approach for efficientlyproducing a wide range of nanoscale particles with a selectedcomposition and a narrow distribution of average particle diameters.Alternatively, submicron particles can be produced using a flameproduction apparatus such as the apparatus described in U.S. Pat. No.5,447,708 to Helble et al., entitled “Apparatus for Producing NanoscaleCeramic Particles,” incorporated herein by reference. Furthermore,submicron particles can be produced with a thermal reaction chamber suchas the apparatus described in U.S. Pat. No. 4,842,832 to Inoue et al.,“Ultrafine Spherical Particles of Metal Oxide and a Method for theProduction Thereof,” incorporated herein by reference. In addition,various solution-based approaches can be used to produce submicronparticles, such as sol gel techniques.

Highly uniform particles can be formed by radiation based pyrolysis,e.g., laser pyrolysis, which can be used to form submicron particleswith extremely uniform properties with a variety of selectablecompositions. For convenience, radiation based pyrolysis is referred toas laser pyrolysis since this terminology reflects the convenience oflasers as a radiation source. Laser pyrolysis approaches discussedherein incorporate a reactant flow that can involve vapors, aerosols orcombinations thereof to introduce desired elements into the flow stream.The versatility of generating a reactant stream with vapor and/oraerosol precursors provides for the generation of particles with a widerange of potential compositions.

Small particles can provide processing advantages with respect toforming small structures and smooth surfaces. In addition, smallparticles have desirable properties for optical applications including,for example, a shifted absorption spectrum and reduced scattering, whichresults in lower scattering loss. Thus, small particle exhibitobservable quantum effects due to their small size, which can affect theoptical properties of corresponding polymer-inorganic particle blends.

A collection of submicron/nanoscale particles may have an averagediameter for the primary particles of less than about 500 nm, preferablyfrom about 2 nm to about 100 nm, alternatively from about 2 nm to about75 nm, or from about 2 nm to about 50 nm. A person of ordinary skill inthe art will recognize that other ranges within these specific rangesare covered by the disclosure herein. Particle diameters are evaluatedby transmission electron microscopy.

The primary particles can have a roughly spherical gross appearance, orthey can have rod shapes, plate shapes or other non-spherical shapes.Upon closer examination, crystalline particles generally have facetscorresponding to the underlying crystal lattice. Amorphous particlesgenerally have a spherical aspect. Diameter measurements on particleswith asymmetries are based on an average of length measurements alongthe principle axes of the particle.

Because of their small size, the primary particles tend to form looseagglomerates due to van der Waals and other electromagnetic forcesbetween nearby particles. These agglomerates can be dispersed in adispersant to a significant degree based on the primary particles, andin some embodiments essentially completely to form dispersed primaryparticles. The size of the dispersed particles can be referred to as thesecondary particle size. The primary particle size, of course, is thelower limit of the secondary particle size for a particular collectionof particles, so that the average secondary particle size preferably isapproximately the average primary particle size. The secondary oragglomerated particle size may depend on the subsequent processing ofthe particles following their initial formation and the composition andstructure of the particles. In some embodiments, the secondary particleshave an average diameter no more than about 1000 nm, in additionalembodiments no more than about 500 nm, in further embodiments from about2 nm to about 300 nm, in other embodiments about 2 nm to about 100 nm,and alternatively about 2 nm to about 50 nm. A person of ordinary skillin the art will recognize that other ranges within these specific rangesare contemplated and are within the present disclosure. Secondaryparticles sizes within a liquid dispersion can be measured byestablished approaches, such as dynamic light scattering. Suitableparticle size analyzers include, for example, a Microtrac UPA instrumentfrom Honeywell based on dynamic light scattering, a Horiba Particle SizeAnalyzer from Horiba, Japan and ZetaSizer Series of instruments fromMalvern based on Photon Correlation Spectroscopy. The principles ofdynamic light scattering for particle size measurements in liquids arewell established.

Even though the particles form loose agglomerates, the nanometer scaleof the primary particles is clearly observable in transmission electronmicrographs of the particles. The particles generally have a surfacearea corresponding to particles on a nanometer scale as observed in themicrographs. Furthermore, the particles can manifest unique propertiesdue to their small size and large surface area per weight of material.For example, the absorption spectrum of crystalline, nanoscale TiO₂particles is shifted, as described in the examples below.

The primary particles can have a high degree of uniformity in size.Laser pyrolysis generally results in particles having a very narrowrange of particle diameters. Furthermore, heat processing under suitablymild conditions does not alter the very narrow range of particlediameters. With aerosol delivery of reactants for laser pyrolysis, thedistribution of particle diameters is particularly sensitive to thereaction conditions. Nevertheless, if the reaction conditions areproperly controlled, a very narrow distribution of particle diameterscan be obtained with an aerosol delivery system. As determined fromexamination of transmission electron micrographs, the primary particlesgenerally have a distribution in sizes such that at least about 95percent, and preferably 99 percent, of the primary particles have adiameter greater than about 40 percent of the average diameter and lessthan about 160 percent of the average diameter. Preferably, the primaryparticles have a distribution of diameters such that at least about 95percent, and preferably 99 percent, of the primary particles have adiameter greater than about 60 percent of the average diameter and lessthan about 140 percent of the average diameter. A person of ordinaryskill in the art will recognize that other ranges within these specificranges are covered by the disclosure herein.

Furthermore, in preferred embodiments no primary particles have anaverage diameter greater than about 4 times the average diameter andpreferably 3 times the average diameter, and more preferably 2 times theaverage diameter. In other words, the particle size distributioneffectively does not have a tail indicative of a small number ofparticles with significantly larger sizes. This is a result of the smallreaction region and corresponding rapid quench of the particles. Aneffective cut off in the tail of the size distribution indicates thatthere are less than about 1 particle in 10⁶ have a diameter greater thana specified cut off value above the average diameter. High particleuniformity can be exploited in a variety of applications. In particular,high particle uniformity can lead to well controlled optical properties.

In addition, the nanoparticles for incorporation into the blends mayhave a very high purity level. Furthermore, crystalline nanoparticles,such as those produced by laser pyrolysis, can have a high degree ofcrystallinity. Similarly, the crystalline nanoparticles produced bylaser pyrolysis can be subsequently heat processed to improve and/ormodify the degree of crystallinity and/or the particular crystalstructure. Impurities on the surface of the particles may be removed byheating the particles to achieve not only high crystalline purity buthigh purity overall.

A basic feature of successful application of laser pyrolysis for theproduction of desirable inorganic nanoparticles is the generation of areactant stream containing one or more metal/metalloid precursorcompounds, a radiation absorber and, in some embodiments, a secondaryreactant. The secondary reactant can be a source of non-metal/metalloidatoms, such as oxygen, required for the desired product and/or can be anoxidizing or reducing agent to drive a desired product formation. Asecondary reactant is not needed if the precursor decomposes to thedesired product under intense light radiation. Similarly, a separateradiation absorber is not needed if the metal/metalloid precursor and/orthe secondary reactant absorb the appropriate light radiation. Thereaction of the reactant stream is driven by an intense radiation beam,such as a light beam, e.g., a laser beam. As the reactant stream leavesthe radiation beam, the particles are rapidly quenched.

A laser pyrolysis apparatus suitable for the production of commercialquantities of particles by laser pyrolysis has been developed using areactant inlet that is significantly elongated in a direction along thepath of the laser beam. This high capacity laser pyrolysis apparatus,e.g., 1 kilogram or more per hour, is described in U.S. Pat. No.5,958,348, entitled “Efficient Production Of Particles By ChemicalReaction,” incorporated herein by reference. Approaches for the deliveryof aerosol precursors for commercial production of particles by laserpyrolysis is described in copending and commonly assigned U.S. Pat. No.6,193,936 to Gardner et al., entitled “Reactant Delivery Apparatus,”incorporated herein by reference.

In general, nanoparticles produced by laser pyrolysis can be subjectedto additional processing to alter the nature of the particles, such asthe composition and/or the crystallinity. For example, the nanoparticlescan be subjected to heat processing in a gas atmosphere prior to use.Under suitably mild conditions, heat processing is effective to modifythe characteristics of the particles without destroying the nanoscalesize or the narrow particle size distribution of the initial particles.For example, heat processing of submicron vanadium oxide particles isdescribed in U.S. Pat. No. 5,989,514 to Bi et al., entitled “ProcessingOf Vanadium Oxide Particles With Heat,” incorporated herein byreference.

A wide range of simple and complex submicron and/or nanoscale particleshave been produced by laser pyrolysis with or without additional heatprocessing. In embodiments of particular interest for the formation ofpolymer-inorganic particle blends, the inorganic particles generallyinclude metal or metalloid elements in their elemental form or incompounds. Specifically, the inorganic particles can include, forexample, elemental metal or elemental metalloid, i.e. un-ionizedelements such as silver and silicon, metal/metalloid oxides,metal/metalloid nitrides, metal/metalloid carbides, metal/metalloidsulfides or combinations thereof. In addition, there is the capabilityfor producing nano-particulate carbon materials. Complex systems ofternary and quaternary compounds have also been made. In addition,uniformity of these high quality materials is substantial. Theseparticles generally have a very narrow particle size distribution, asdescribed above. Availability of multiple types of nanoparticlesprovides a significant increase in potential combinations betweennanoparticles and polymers.

With respect to the electrical properties of the particles, someparticles include compositions such that the particles are electricalconducting, electrical insulators or electrical semiconductors. Suitableelectrical conductors include, for example, elemental metals and somemetal compositions. Electrical conductors, such as metals, generallyhave a room temperature resistivity of no more than about 1×10⁻³ Ohm-cm.Electrical insulators generally have a room temperature resistivity ofat least about 1×10⁵ Ohm-cm. Electrical semiconductors include, forexample, silicon, CdS and InP. Semiconducting crystals can be classifiedto include so called, II–VI compounds, III–V compounds and group IVcompounds, where the number refers to the group in the periodic table.Semiconductors are characterized by a large increase in conductivitywith temperature in pure form and an increase in electrical conductivityby orders of magnitude upon doping with electrically active impurities.Semiconductors generally have a band gap that results in the observedconductivity behavior. At room temperature, the conductivity of asemiconductor is generally between that of a metal and a good electricalinsulator.

Several different types of nanoscale particles have been produced bylaser pyrolysis. As used herein, inorganic particles include carbonparticles as carbonaceous solids, such as fullerenes, graphite, andcarbon black. Such nanoscale particles for light reactive deposition cangenerally be characterized as comprising a composition with a number ofdifferent elements that are present in varying relative proportions,where the number and the relative proportions are selected based on theapplication for the nanoscale particles. Materials that have beenproduced (possibly with additional processing, such as a heat treatment)or have been described in detail for production by laser pyrolysisinclude, for example, carbon particles, silicon, amorphous SiO₂, dopedSiO₂, crystalline silicon dioxide, titanium oxide (anatase and rutileTiO₂), MnO, Mn₂O₃, Mn₃O₄, Mn₅O₈, vanadium oxide silver vanadium oxide,lithium manganese oxide, aluminum oxide (γ-Al₂O₃, delta-Al₂O₃ andtheta-Al₂O₃), doped-crystalline and amorphous alumina, tin oxide, zincoxide, rare earth metal oxide particles, rare earth dopedmetal/metalloid oxide particles, rare earth metal/metalloid sulfides,rare earth doped metal/metalloid sulfides, silver metal, iron, ironoxide, iron carbide, iron sulfide (Fe_(1-x)S), cerium oxide, zirconiumoxide, barium titanate (BaTiO₃), aluminum silicate, aluminum titanate,silicon carbide, silicon nitride, and metal/metalloid compounds withcomplex anions, for example, phosphates, silicates and sulfates. Inparticular, many materials suitable for the production of opticalmaterials can be produced by laser pyrolysis. The production ofparticles by laser pyrolysis and corresponding deposition as a coatinghaving ranges of compositions is described further in copending andcommonly assigned U.S. patent application Ser. No. 10/027,906, now U.S.Pat. No. 6,952,504 to Bi et al., entitled “Three Dimensional Engineeringof Optical Structures,” incorporated herein by reference.

Submicron and nanoscale particles can be produced with selected dopantsusing laser pyrolysis and other flowing reactor systems. Amorphouspowders and crystalline powders can be formed with complex compositionscomprising a plurality of selected dopants. The powders can be used toform optical materials and the like. Amorphous submicron and nanoscalepowders and glass layers with dopants, such as rare earth dopants and/orother metal dopants, are described further in copending and commonlyassigned U.S. Provisional Patent Application Ser. No. 60/313,588 to Homeet al., entitled “Doped Glass Materials,” incorporated herein byreference. Crystalline submicron and nanoscale particles with dopants,such as rare earth dopants, arc described further in copending andcommonly assigned U.S. patent application Ser. No. 09/843,195, now U.S.Pat. No. 6,692,660 to Kutnar et al., entitled “High LuminescencePhosphor Particles,” incorporated herein by reference.

The dopants can be introduced at desired quantities by varying thecomposition of the reactant stream. The dopants are introduced into anappropriate host material by appropriately selecting the composition inthe reactant stream and the processing conditions. Thus, submicronparticles incorporating one or more metal or metalloid elements as hostcomposition with selected dopants, including, for example, rare earthdopants arid/or complex blends of dopant compositions, can be formed.For embodiments in which the host materials are oxides, an oxygen sourceshould also be present in the reactant stream. For these embodiments,the conditions in the reactor should be sufficiently oxidizing toproduce the oxide materials.

Furthermore, dopants can be introduced to vary properties of theresulting particles. For example, dopants can be introduced to changethe index-of-refraction of the particles that are subsequentlyincorporated into the polymer-inorganic particle blend. For opticalapplications, the index-of -refraction can be varied to form specificoptical devices that operate with light of a selected frequency range.Dopants can also be introduced to alter the processing properties of thematerial. Furthermore, dopants can also interact within the materials.For example, some dopants are introduced to increase the solubility ofother dopants.

In some embodiments, the one or plurality of dopants are rare earthmetals or rare earth metals with one or more other dopant elements. Rareearth metals comprise the transition metals of the group IIIb of theperiodic table. Specifically, the rare earth elements comprise Sc, Y andthe Lanthanide series. Other suitable dopants comprise elements of theactinide series. For optical glasses, the rare earth metals ofparticular interest as dopants comprise, for example, Ho, Eu, Ce, Tb,Dy, Er, Yb, Nd, La, Y, Pr and Tm. Generally, the rare earth ions ofinterest have a +3 ionization state, although Eu⁺² and Ce⁺⁴ are also ofinterest. Rare earth dopants can influence the optical absorptionproperties that can alter the application of the materials for theproduction of optical amplifiers and other optical devices. Suitablenon-rare earth metal dopants for optical glasses comprise, for example,Bi, Sb, Zr, Pb, Li, Na, K, Ba, B, Ge, W, Ca, Cr, Ga, Al, Mg, Sr, Zn, Ti,Ta, Nb, Mo, Th, Cd and Sn.

In addition, suitable metal oxide dopants for aluminum oxide for opticalglass formation comprise cesium oxide (Cs₂O), rubidium oxide (Rb₂O),thallium oxide (Ti₂O), lithium oxide (Li₂O), sodium oxide (Na₂O),potassium oxide (K₂O), beryllium oxide (BeO), magnesium oxide (MgO),calcium oxide (CaO), strontium oxide (SrO) and barium oxide (BaO).Aluminum oxide dopants can affect, for example, the index-of-refraction,consolidation temperature and/or the porosity of the glass. Suitablemetal oxide dopants for infrared emitters comprise, for example, cobaltoxide (Co₃O₄), Er₂O₃, CrO₂, Tm₂O₃, Nd₂O₃, Yb₂O₃, Pr₂O₃, Dy₂O₃, andHo₂O₃.

As noted above, laser pyrolysis has been used to produce a range ofpowder compositions. The compositions can include multiplemetal/metalloid elements. A representative sample of references relatingto some of these powder materials are presented.

As a first example of nanoparticle production, the production of siliconoxide nanoparticles is described in copending and commonly assigned U.S.patent application Ser. No. 09/085,514, now U.S. Pat. No. 6,726,990 toKumar et at., entitled “Silicon Oxide Particles.” incorporated herein byreference. This patent application describes the production of amorphousSiO₂. The synthesis by laser pyrolysis of silicon carbide and siliconnitride is described in copending and commonly assigned U.S. patentapplication Ser. No. 09/433,202 to Reitz et al. filed on Nov. 5, 1999,entitled “Particle Dispersions,” incorporated herein by reference. Theproduction of silicon particles by laser pyrolysis is described in anarticle by Cannon et al., J. of the American Ceramic Society. Vol. 65,No. 7, pp. 330–335 (1982), entitled Sinterable Ceramic Particles FromLaser-Driven Reactions: II, Powder Characteristics And ProcessVariables,” incorporated herein by reference.

The production of titanium oxide nanoparticles and crystalline silicondioxide nanoparticles is described in copending and commonly assigned,U.S. patent application Ser. No. 09/123,255, now U.S. Pat. No. 6,387,531to Bi et al., entitled “Metal (Silicon) Oxide/Carbon Composites,”incorporated herein by reference. In particular, this applicationdescribes the production of anatase and rutile TiO₂. The production ofaluminum oxide nanoparticles is described in copending and commonlyassigned, U.S. patent application Ser. No. 09/136,483 to Kumar et at.,entitled “Aluminum Oxide Particles.” incorporated herein by reference.In particular, this application disclosed the production of γ-Al₂O₃.Suitable liquid, aluminum precursors with sufficient vapor pressure ofgaseous delivery include, for example, aluminum s-butoxide (Al(OC₄H₉)₃).Also, a number of suitable solid, aluminum precursor compounds areavailable including, for example, aluminum chloride (AlCl₃), aluminumethoxide (Al(OC₂H₅)₃), and aluminum isopropoxide (Al[OCH(CH₃)₂]₃).

Furthermore, mixed metal oxide nanoparticles have been produced by laserpyrolysis along with or without subsequent heat processing, as describedin copending and commonly assigned U.S. patent applications Ser. No.09/188,768, now U.S. Pat. No. 6,607,706 to Kumar et al., entitled“Composite Metal Oxide Particles,” and Ser. No. 09/334,203, now U.S.Pat. No. 6,482,374 to Kumar et al., entitled “Reaction Methods forProducing Ternary Particles,” and U.S. Pat. No. 6,136,287 to Home etal., entitled “Lithium Manganese Oxides and Batteries,” all three ofwhich are incorporated herein by reference. The formation of submicronand nanoscale particles comprising metal/metalloid compounds withcomplex anions is described in copending and commonly assigned U.S.patent application Ser. No. 09/845,985 to Chaloner-Gill et al., entitled“Phosphate Powder Compositions And Methods For Forming Particles WithComplex Anions,” incorporated herein by reference. Suitable complexanions include, for example, phosphates, silicates and sulfates.

Formation of Polymer-Inorganic Particle Blends

Formation of the blends involves distributing the particles within thepolymer material such that the resulting blend forms a single material.The polymerization process can be performed before combining theparticles with the polymer materials or in the presence of the inorganicparticles or some combination thereof. The process for forming aparticular blend generally depends on whether the particles are simplydispersed within a polymer matrix binder as a mixture or whether atleast some of the particles are covalently bonded to the polymer as acomposite. The process for forming the blend may involve dispersing theinorganic particles, especially for the formation of composites. If acomposite is formed a linker molecule may be used to join the polymerand the inorganic particle. The order for bonding the linker, theinorganic particles and the polymer can be selected to yield aconvenient process.

The formation of a particle dispersion provides for the separation ofthe particles such that the particles can be well dispersed within theresulting blend. The use of a dispersion can result in a more uniformblend with the particles approximately uniformly distributed through theblend. The solvent, pH, ionic strength and additives can be selected toimprove the dispersion of the particles. Greater dispersion of theparticles and stability of the dispersions helps to reduce agglomerationof the particles in the resulting blend.

However, in alternative embodiments, the powders can be ground orotherwise directly mixed with the polymer to disperse the particlesthrough the polymer. Mixing can be performed with or without thepresence of a solvent/dispersant. Commercial mixers or grinders, forexample, can be used to form the particle-polymer mixtures. Heat,pressure and/or solvent/dispersant removal can be used to bind particleswithin a polymer mixture in which the polymer functions as a binder.Although at high particle loadings in a mixture, the particles may behighly aggregated, unless possibly if the particles were well dispersedprior to and during formation of the mixture.

In some embodiments, the formation of a particle dispersion can be adistinct step of the process. Preferably, a collection of particles,e.g., nanoparticles, is well dispersed for uniform introduction into apolymer blend, e.g., a composite. A liquid phase particle dispersion canprovide a source of small secondary particles that can be used in theformation of desirable blend structures. Desirable qualities of a liquiddispersion of inorganic particles generally depend on the concentrationof particles, the composition of the dispersion and the formation of thedispersion. Specifically, the degree of dispersion intrinsically dependson the interparticle interactions, the interactions of the particleswith the liquid and the surface chemistry of the particles. Suitabledispersants include, for example, water, organic solvents, such asalcohols and hydrocarbons, and combinations thereof. The selection ofappropriate dispersants/solvents generally depends on the properties ofthe particles. The degree of dispersion and stability of the dispersioncan be significant features for the production of uniform compositeswithout large effects from significantly agglomerated particles.

Generally, the liquid dispersions refer to dispersions having particleconcentrations of no more than about 80 weight percent. For theformation of a particle dispersion, the particular particleconcentration depends on the selected application. At concentrationsgreater than about 50 weight percent, different factors can besignificant with respect to the formation and characterization of theresulting viscous blend relative to parameters that characterize themore dilute particle dispersions. The concentration of particles affectsthe viscosity and can affect the efficacy of the dispersion process. Inparticular, high particle concentrations can increase the viscosity andmake it more difficult to disperse the particles to achieve smallsecondary particle sizes, although the application of shear can assistwith particle dispersion.

Since many polymers are soluble in organic solvents, many embodimentsinvolve the formation of non-aqueous dispersions. In addition, waterbased dispersions can include additional compositions, such assurfactants, buffers and salts. For particular particles, the propertiesof the dispersion can be adjusted by varying the pH and/or the ionicstrength. Ionic strength can be varied by addition of inert salts, suchas sodium chloride, potassium chloride or the like. The presence of thelinker can effect the properties and stability of the dispersion. The pHgenerally affects the surface charge of the dispersed particles. Theliquid may apply physical/chemical forces in the form of solvation-typeinteractions to the particles that may assist in the dispersion of theparticles. Solvation-type interactions can be energetic and/or entropicin nature.

The qualities of the dispersion generally depend on the process for theformation of the dispersion. In dispersions, besides chemical/physicalforces applied by the dispersant and other compounds in the dispersion,mechanical forces can be used to separate the primary particles, whichare held together by van der Waals forces and other short rangeelectromagnetic forces between adjacent particles. In particular, theintensity and duration of mechanical forces applied to the dispersionsignificantly influences the properties of the dispersion. Mechanicalforces can be applied to the powders prior to dispersion in a solvent.Alternatively, mechanical forces, such as shear stress, can be appliedas mixing, agitation, jet stream collision and/or sonication followingthe combination of a powder or powders and a liquid or liquids. Smallersecondary particles sizes are obtained if there is more disruption ofthe agglomerating forces between the primary particles.

The presence of small secondary particle sizes, e.g., close to theprimary particle size, can result in significant advantages in theapplication of the dispersions for the formation of blends with uniformproperties. For example, smaller secondary particle sizes, and generallysmall primary particle sizes, may assist with the formation of smootherand/or smaller and more uniform structures using the blends. In theformation of coatings, thinner and smoother coatings can be formed withblends formed with inorganic particle dispersions having smallersecondary particles.

Once the dispersion is formed, the dispersion may eventually separatesuch that the particles collect on the bottom of the container withoutcontinued mechanical stirring or agitation. Stable dispersions haveparticles that do not separate out of the dispersion. Differentdispersions have different degrees of stability. The stability of adispersion depends on the properties of the particles, the othercompositions in the dispersion, the processing used to form thedispersion and the presence of stabilizing agents. Suitable stabilizingagents include, for example, surfactants. In some embodiments,dispersions are reasonably stable, such that the dispersions can be usedwithout significant separation during the subsequent processing stepsforming the blends, although suitable processing to form a blend can beused involving constant mixing or the like to prevent separation of theparticle dispersion.

For the formation of composites, during formation or after formation ofthe particle dispersion, the dispersion is interacted with the linkermolecules and/or the polymer. To form the desired composites, theinorganic particles may be modified on their surface by chemical bondingto one or more linker molecules. Generally, for embodiments involving alinker, the linker is soluble in the liquid used to form the inorganicparticle dispersion and/or the polymer dispersion so that the linker issubstantially homogeneously dissolved when bonding from solution.Conditions for the combined particle dispersion and polymerdispersion/solution can be suitable for the formation of bonds betweenthe linker, the inorganic particles and the polymer. The order foradding the linker to the inorganic particles and the polymer can beselected to achieve the desired processing effectiveness. Oncesufficient time has passed to complete the bonding between thecomponents of the composite, the composite can be processed further.

The ratio of linker composition to inorganic particles preferably is atleast one linker molecular per inorganic particle. The linker moleculessurface modify the inorganic particles, i.e., functionalize theinorganic particles. While the linker molecules bond to the inorganicparticles, they are not necessarily bonded to the inorganic particlesprior to bonding to the polymers. They can be bonded first to thepolymers and only then bonded to the particles. Alternatively, thecomponents can be blended such that bonding between the linker and thetwo species occurs simultaneously.

The linker compound and the polymer/monomer components can be added tothe liquid with the particle dispersion simultaneously or sequentially.The order of combining the various constituents can be selected toachieve the desired results. The conditions within the liquid preferablyare suitable for the bond formation with the linker and possibly otherbond formation involving the polymer/ monomer constituents. Once thecomposite is formed, the liquid can be removed or solidified to leavebehind a structure formed from the composite.

The polymer/monomer composition can be formed into a solution/dispersionprior to addition to the inorganic particle dispersion, or thepolymer/monomer can be added as a solid to the particle dispersion. Inpreferred embodiments, the polymer/monomer compositions are soluble inthe liquid used to form the particle dispersion. If the polymer/monomeris not soluble/dispersible in the particle dispersion, either thepolymer/monomer solution or the particle dispersion is slowly added tothe other while mixing to effect the reaction. Whether or not thepolymer/monomer is first solubilized separate from the inorganicparticle dispersion may depend on the kinetics of the polymer/monomersolubilization and on the desired concentrations of the varioussolutions/dispersions. Similarly, bonding kinetics can influence theorder and details of the mixing procedures.

In some embodiments, the reaction conditions and/or the presence of acatalyst or the like is needed to initiate the reaction of the linkerwith the inorganic particle and/or the polymer/monomer. In theseembodiments, the components can be mixed prior to the adjustment of thereaction conditions of the addition of a catalyst. Thus, a well mixedsolution/dispersion can be formed prior to the adjustment of thereaction conditions or addition of the catalyst to form a more uniformcomposite.

Structures Incorporating Polymer-Inorganic Particle Blends

While the blends can be formed into free standing structures, structuresof interest can involving interfaces between a polymer-inorganicparticle blend and another material. The other material at the interfacemay or may not itself be a polymer-inorganic particle blend. Theinterface can be along a planar surface, along an edge of an extendedmaterial and/or along other types of surface either simple or complex.In some embodiments of interest, the polymer-inorganic particle blend isan optical material. In these embodiments, the other material may alsobe an optical material such that the interface is an optical interface.The interfaces can be incorporated into particular structures to formdevices of interest.

Referring to FIG. 1, structure 100 includes a first layer 102 ofpolymer-inorganic particle blend and a second layer 104 of a secondmaterial. First layer 102 contacts second layer 104 at interface 106. Inthis embodiment, interface 106 is planar, although other non-planarinterfaces of simple or complex geometry can be formed. Additionallayers can be formed from polymer-inorganic particle blends and/or othermaterials. Specifically, the structure can include three or more layerswith adjacent layers having the same or different compositions. Ifadjacent layers both are polymer-inorganic particle blends, the layerscan differ with respect to the polymer, the inorganic particles and/orparticle loadings. In particular, adjacent layers can have differentparticle loadings to adjust the differences in index-of-refractionbetween the adjacent materials. The optical properties within a layerdepend on the index-of-refraction as well as the dimensions including,for example, thickness. Planar structures, such as shown in FIG. 1, havelengths in two dimensions that are at least an order of magnitude, i.e.,a factor of 10, larger than a thickness along a dimension perpendicularto the two extended dimensions.

Referring to FIG. 2, structure 112 has a first material 114 comprising apolymer-inorganic particle blend and a second material 116. Firstmaterial 114 and second material 116 form an interface 118 along anedge. An edge has at least one dimension that is at least an order ofmagnitude smaller than an extended length dimension of the structure. Amore complex structure is depicted in FIG. 3. Structure 124 includes afirst material 126 comprising; a polymer-inorganic particle blend, asecond material 128 and a third material 130. First material 126, secondmaterial 128 and third material 130 contact each other at interfaces132, 134, 136, 138. Various other structures involving polymer-inorganicparticle blends can be formed including, for example, more complexstructures with corresponding complex interfaces between adjacentmaterials and/or structures with a network of interfaces that may formoptical pathways through the structure.

Generally, one of the materials within the structures of interestcomprises a polymer-inorganic particle blend. Suitable relativeproportions and compositions of the components of the blend aredescribed in detail above. Specific compositions can be selected basedon the desired properties, such as index-of-refraction, of the materialwithin the structure. The polymer-inorganic particle blend can be amixture or a composite. Polymer-inorganic particle composites generallyare more stable and have more dispersed inorganic particles comparedwith mixtures, assuming appropriate processes are used to form thecomposites. In addition, a polymer-inorganic particle blend material canfurther comprise, for example, other polymers, such as organic orinorganic polymer particles and/or non-polymer, non-particulate propertymodifiers, for example, viscosity modifiers, antioxidants, plasticizers,dyes and the like. Polymer-inorganic particle composites can alsoinclude polymers that are not bonded to the inorganic polymers orcrosslinked to the polymer bonded to the inorganic particles. Thesenon-bonded polymers may or may not have the same chemical composition asthe polymer bonded to the inorganic particles of the composite.Similarly, a polymer-inorganic particle composite can include non-bondedinorganic particles in addition to the bonded inorganic particles. Thenon-bonded inorganic particles may or may not have the same properties,such as composition, crystallinity, average size and size distribution,as the bonded particles.

The other material(s) in a structure may or may not also bepolymer-inorganic particle blends. For example, the other materials canbe polymers or non-polymer inorganic materials. Specifically, thepolymer may or may not be the same polymer used in an adjacentpolymer-inorganic particle blend. Suitable polymers for incorporatinginto structures include, for example, the polymers that can beincorporated into the blends, as described above. These polymers notformed into blends can be combined with additives, such as viscositymodifiers, plasticizers, antioxidants, dyes and the like. When polymersare placed adjacent polymer-inorganic particle blends, the nature of thepolymers and inorganic particles in the adjacent layers generallydetermines the nature of the interface. With respect to other materialsat the interface, suitable non-polymer inorganic materials include, forexample, elemental metals, metal alloys, metal/metalloid compositions,carbon materials, such as graphite and amorphous carbon, and the like.Non-polymer inorganic materials include crystalline and amorphouscompositions that are not covalently bonded into linear polymer units.For the formation of optical structures, suitable inorganic materialsinclude, for example, TiO₂, SiO₂, GeO₂, Al₂O₃, P₂O₅, B₂O₃, TeO₂, andcombinations, mixtures and doped versions thereof. Non-linear opticalmaterials, such as zinc oxide, KTaO₃, K(Ta,Nb)O₃, YVO₄, cadmium sulfide(CdS), cadmium selenide (CdSe), indium phosphide (InP), lithium niobate(LiNbO₃), and barium titanate (BaTiO₃), can be used within an opticalstructure to modulate the wavelength, e.g., generate harmonics ofincident light, and/or for optical bistable or switch function as afunction of light power resulting from a non-linear power response,which can be desirable in some optical devices. Dopants can be used toincrease the performance of the non-linear optical materials. Suitablecadmium precursors for aerosol delivery into a laser pyrolysis apparatusinclude, for example, CdCl₂, and Cd(NO₃)₂, and suitable indiumprecursors for aerosol delivery into a laser pyrolysis apparatusinclude, for example, indium trichloride (InCl₃). In addition, smallcrystalline nanoparticles, e.g., no more than about 20 nm, can exhibitnon-linear properties due to imperfections that result in a loss ofinversion symmetry. These symmetry-breaking effects are enhanced due tothe small particle size. Thus, small nanoparticles, such as crystallinesilicon, can be used to take advantage of non-linear optical effects.For optical applications, it is desirable to have materials with largesecond order and/or third order electrical susceptabilities (χ⁽²⁾ andχ⁽³⁾) to obtain larger optical non-linearity effects.

One or more materials within the structures can be an optical material.In particular, one or more optical materials can be incorporated withinthe structures such that the structure is an optical structure. Opticalstructures can incorporate one or more optical devices, that can be usedto transmit and or manipulate light within the structure. As usedherein, an optical material includes materials that can transmit light,with selected wavelengths, with low lass due to scattering andabsorption. In particular, for transmission applications, opticalmaterials have a propogation loss at a particular wavelength in theinfrared, visible or ultraviolet of no more than about 20 percent over 1centimeter, although desirable materials have significantly lowerpropagation losses. Useful optical materials can be absorbing at somewavelengths and transmitting at other wavelengths. For example,amplifiers materials can absorb in ultraviolet and/or visible andtransmit in the visible or infrared. In other embodiments, opticalmaterials emit at desired frequencies upon excitation by absorption orelectrical stimulation. Thus, phosphors and the like can be incorporatedinto polymer-inorganic particle blends. Nanoparticle phosphors aredescribed further in copending and commonly assigned U. S. patentapplication Ser. No. 09/843,195, now U.S. Pat. No. 6,692,660 to Kumar etal., entitled “High Luminescent Phosphors,” incorporated herein byreference. In some embodiments, phosphors include a host crystal ormatrix and a small amount of activator. Suitable host materials for theformation of phosphors include, for example, ZnO, ZnS, Zn₂SiO₄, SrS,YBO₃, Y₂O₃, Al₂O₃, Y₃Al₅O₁₂ and BaMgAl₁₄O₂₃. Generally, heavy metal ionsor rare earth ions are used as activators.

In particular, in some embodiments of interest, the polymer-inorganicparticle blend is an optical material. Generally, the composition of thepolymer and the inorganic particles are selected appropriately to forman optical material with desired optical properties. Similarly, theparticle loadings are selected to yield desired optical properties ofthe resulting blend. In preferred embodiments, the blend is a compositeto provide desired amounts of stability at high particle loadings duringprocessing into desired structures.

The polymer-inorganic particle blends provide for continuous selectionof index-of-refraction over wide ranges. The index-of-refraction of theblend generally is expected to be approximately a linear combination bythe weight ratios of the index-of-refraction of the inorganic particlesand the polymer. Any non-linearities in the dependence ofindex-of-refraction as a function of particle loadings can be accountedfor empirically based on measurements of the index-of-refraction. Toform high index-of-refraction materials, high particle loadings aregenerally used with the inorganic particles correspondingly beingselected for a high index-of-refraction. Thus, the pure polymergenerally would provide the lower limit on the index-of-refraction forthe blend. The upper limit on the index-of-refraction for a blend as afunction of particle loading would be the index value at the highestparticle loadings. Specifically, TiO₂ generally has a highindex-of-refraction with values ranging from about 2.5 to about 2.9. InPand other phosphides, for example, have indices-of-refraction greaterthan 3. SiO₂ generally has a relatively low index-of-refraction fromabout 1.45 to about 1.5. Suitable polymers generally have a low index ofrefraction from about 1.3 to about 1.6. Thus, polymer-inorganic particleblends can be formed with an index-of-refraction up to 2.7 or more. Withinterfaces between a polymer-inorganic particle blend and a polymer oranother polymer-inorganic particle blend, the differences inindex-of-refraction can be as small as desired or, in some embodiments,from 0.001 to about 1.5 or more.

The use of nanoparticles within the blends has the advantage for opticalmaterials of higher transparency and reduced scattering of lightrelative to optical properties of corresponding blends when using largerinorganic particles. Nanoparticles are especially effective in reducingscattering in the infrared portion of the electromagnetic spectrumincluding wavelengths of about 0.8 microns to about 5.0 microns. Thus,polymer-inorganic particle blends formed with the nanoparticles willhave correspondingly lower scattering.

For embodiments in which the polymer-inorganic particle material is anoptical material, the adjacent material at the interface can also be anoptical material such that an optical interface is formed. The otheroptical material at the interface can be a polymer, a polymer-inorganicparticle blend or a uniform inorganic material. Polymers can be usedespecially to form a low index-of-refraction material. Polymer-inorganicparticle blends can be used to incorporate desired index differencesbetween the materials at the interface and to incorporate desiredoptical properties to the second material. Suitable uniform inorganicmaterials include, for example, optical glasses, such as silica glassesand doped silica glasses, and crystalline or polycrystalline materials,such as quartz.

The difference in index-of-refraction between the two materials at theinterface generally is selected to form a desired device incorporatingthe structure. In general, the difference in index-of-refraction is atleast about 0.0025, in other embodiments at least about 0.005, and infurther embodiments at least about 0.01. In some embodiments, relativelysmall differences are sufficient to confine the light and to control thepropagation modes. In alternative embodiments, a larger difference inindex-of-refraction is used to obtain desired functionality. Thus, itmay be desirable to have a difference in value of theindex-of-refraction between the two materials at least about 0.05, infurther embodiments at least about 0.1, in other embodiments from about0.2 to about 2.5 and in further embodiments from about 0.5 to about 2.0.A person of ordinary skill in the art will recognize that other valuesfor the differences in value of index-of-refraction between theseexplicit differences are contemplated and are within the presentdisclosure.

The transition between two materials with differentindices-of-refraction can be formed with a gradual or continuous changebetween the materials. The reflection is a function of the difference inindex-of-refraction between two materials at an interface. Theevaluation of transmission and reflection at an interface between twooptical materials with different indices-of-refraction can be calculatedusing well known optical formulas. Since the function is non-linear,i.e., quadratic, with respect to the index-difference, the loss due toreflection at the interface can be reduced or eliminated. This reductionin reflection can be especially significant for transitions betweenmaterials with a large difference in index-of-refraction between the twomaterials.

The optical interfaces can be used to form optical devices with simpleor complex structures and/or functionalities. For example, thepolymer-inorganic particle blends can be used to form passive opticaldevices such as waveguides/optical channels and couplers/splitters andthe like. The polymer-inorganic particle blends can be used for the coreand/or for the cladding of the devices. The waveguides and the like, forexample, can be within an optical fiber or on a planar opticalstructure. Referring to FIG. 4, waveguide 140 has a core 142 surroundedby cladding 144. Generally, core 142 has a higher index-of-refractionthan cladding 144 such that light is confined within the core by totalinternal reflection. The difference in index-of-refraction can beselected to limit the modes of transmission of light at a particularwavelength. If the core and cladding are both formed frompolymer-inorganic particle blends, the difference in index-of-refractioncan be timed by selecting the particle loading, composition of thepolymer and/or composition and other properties of the inorganicparticles. Referring to FIGS. 5 and 6, a coupler/splitter 146 is shownwith a core material 148 surrounded by cladding 150. Appropriatedimensions of the core orthogonal to the propagation direction depend onthe index-of-refraction and the wavelength of light. Generally, however,the dimensions across the cross section of a waveguide are within anorder of magnitude of the wavelength of light. Thus, for most opticalapplications, the light channels have dimensions less than about 10microns.

In planer embodiments of optical structures, waveguides and comparableelements, such as those in FIGS. 4–6, have a layered structure,generally on a substrate. In these embodiments, a polymer-inorganicparticle blend can be used as an over-cladding on top of core and/orunder-cladding of a uniform inorganic optical material, such as a silicaglass, to form an a thermal waveguide. In particular, the presence ofthe polymer-inorganic particle blend can compensate for thermal stresseswithin the structure if the index-of-refraction of the polymer-inorganicparticle blend is selected to account for index of refraction changes inthe structure due to the presence of thermal stress.

The polymer-inorganic particle blends and corresponding interfaces witha second material can be incorporated into devices of interest. Suitabledevices can be optical devices. Devices that can be formed withpolymer-inorganic particle blends include, for example, interconnects,reflectors, displays, micro-electromechanical structures (MEMS), tunablefilters and optical switches. MEMS structures can be incorporated intooptical devices, for example, to adjust distances between components.Other devices of interest have periodic variations inindex-of-refraction, as described below.

Low loss interconnects are depicted in FIGS. 7A and 7B. Referring toFIG. 7A interconnect 151 comprises a core 152 within cladding 153. Core152 connects a first, high index, material 154 with a second, low index,material 155. Core 152 further comprises an interconnect transition 156.Interconnect transition 156 comprises a one or more layers 157 withindices-of-refraction intermediate between the index of first material154 and second material 155. Layers 157 have a gradual, monotonic,transition in index-of-refraction with a higher index-of-refractiontoward first material 154 and a lower index-of-refraction toward secondmaterial 155. The thickness and number of layers can be selected toreduce the loss to arbitrarily small values due to reflection of lighttransmitted between first material 154 and second material 155. Bymaking the layers smaller and increasing the number of layers,interconnect transition can be made to approximate a continuoustransition in index with a loss approaching zero. Interconnecttransition 157 can be formed from polymer-inorganic particle blends. Theindex can be changed conveniently in a step-wise way or, alternatively,continuous way by altering the particle loading, although the index canalso be altered by changing the composition of the polymer and/orinorganic particles. First material 154 and second material 155 can eachbe an optical polymer, a polymer-inorganic particle blends or adensified inorganic optical material, such as a doped silicon oxideglass.

With an change in index-of-refraction, appropriate cross-sectional areasof the core region of a waveguide, either fiber or planar, can bealtered without changing the propagation of the light. In particular,with an increase in index-of-refraction, the core can be made thinnerand/or narrower. The interconnect can then correspondingly change sizegradually or step-wise along with the change in index-of-refraction.Referring to FIG. 7B, interconnect core 131 connects between high indexcore 133 and low index core 135. As shown in FIG. 7B, interconnect core131 gradually tapers in thickness from a thinner dimension adjacent highindex core 133, which is correspondingly thinner than low index core133, to a thicker dimension adjacent low index core 135. The index ofrefraction can change in a continuous or step-wise way. Similarly, inalternative embodiments, the thickness of interconnect core 131 canchange in a step-wise way. Interconnect cladding 137, thinner cladding139 and thicker cladding 141 can be formed all from the same material,with the same index-of-refraction, or from different material, withcorrespondingly different indices-of-refraction. Interconnect cladding137 can change in thickness and/or index-of-refraction in a step-wise orcontinuous way.

In addition, the polymer-inorganic particle blends can be used as a gluebetween two other optical materials. The polymerization and/orcrosslinking can be completed following application of the blend as aninterconnect between two materials. Completion of thepolymerization/crosslinking can physically connect the two materials andprovide a continuous optical path. The index-of-refraction of thepolymer-inorganic particle blend can be selected, as described herein,to approximately match the other materials to reduce the loss. Due tohigh available particle loadings the optical glue can have a highindex-of-refraction. Polymer alone or a lower index polymer-inorganicparticle blend can be added as a cladding that polymerizes orcrosslinked to completion following application to further assist withthe physical binding of the materials. Such an embodiment is shown inFIG. 8. Core glue 161 and cladding glue 163 connect first opticalconduit 165 and second optical conduit 167. Core glue 161 comprisespolymer-inorganic particle blend.

Light is generally transmitted through waveguides due to total internalreflection since the core has a higher index-of-refraction than thesurrounding cladding. Loss can occur due to bending of the core if theindex-difference between the core and cladding is not large enough toconfine the light within the core at the angles of incidence at thebend. If the difference in index-of-refraction between the core and thecladding is larger, sharper bends in the core can be made withoutincurring loss in optical transmission. The polymer-inorganic particleblends can be formed with a relatively high index-of-refraction, asdescribed above, such that a larger difference in index between the coreand cladding can be formed. An appropriate degree of bending can beevaluated using conventional optical formulas. Thus, bends with agreater angle can be achieved relative to bends involving materials witha lower achievable index-of-refraction. A bend is depicted in FIG. 9.Core 171 is surrounded by cladding 173. The angle at bend 175 can beselected based on the difference in index-of-refraction to yield no lossor an acceptably small loss. Reflectors/bends with sharper angles can beused to form optical devices in a smaller footprint.

Suitable displays include, for example, reflective-type displays. Insome embodiments, the polymer-inorganic particle blends can replaceconventional polymers within a polymer-dispersed liquid crystal display.By selecting the desired index-of- refraction for the polymer-inorganicparticle blend, the index-of refraction can be matched better to theadjacent materials such that less undesirable reflection takes place.With less undesirable reflection, the display element can have a sharperimage. General features of polymer-dispersed liquid crystal displays aredescribed further in U.S. Pat. No. 6,211,931 to Fukao et al., entitled“Polymer-Dispersed Liquid Crystal Composition And Liquid Crystal DisplayElements Using The Composition,” incorporated herein by reference.

A portion of an embodiment of a polymer-dispersed liquid crystal displayis shown in FIG. 10. Display 160 has a first element 162 and a secondelement 164. Each element has a transparent electrode 166 and atransparent counter electrode 168 in a spaced apart configuration.Transparent electrodes can be formed, for example, from indium tinoxide. An outer transparent cover 170 covers the viewing side of display160. A black absorbing layer 172 is located past transparent counterelectrodes 168 on the side of display 160 opposite transparent cover170. Polymer-inorganic particle blend 174 is located between transparentelectrodes 166 and transparent counter electrodes 168. Liquid crystaldroplets 176 are dispersed within blend 172. Liquid crystal droplets 176can be microcapsules or located within voids in the blend. Liquidcrystal droplets can include liquid crystals, such ascyanobiphenyl-based liquid crystals (produced by Merck Corp.) and caninclude dyes.

Electrodes 166, 168 are connected to control circuitry 178 for theselective application of an electric current to electrodes 166, 168thereby generating an electric field between transparent electrodes 166and transparent counter electrodes 168. When current is not applied, theliquid crystals are randomly oriented, as shown in element 162, suchthat incoming light through transparent cover 170 is scattered andelement 162 has a color based on the dye. When an electric field isapplied, the liquid crystals align, as shown in element 164, such thatmore light is transmitted to black absorbing layer 172 and the elementappears dark or off. Thus, when no electricity is applied, the displaylooks white from reflection from all the elements. If thepolymer-inorganic particle blend has an index-of-refraction closer tothe index-of-refraction of the liquid crystal droplets, greater amountsof light can be transmitted to the black absorbing layer whenelectricity is applied such that off elements are darker, i.e., thecontrast between on and off elements can be greater.

The polymer-inorganic particle blends can be incorporated intomicro-electromechanical systems (MEMS), especially for opticalapplications, although non-optical applications are also contemplated.Microelectro-mechanical systems for convenience will be used generallyto refer also to both micron scale systems and submicron scale systems,nanoelectro-mechanical systems. MEMS systems generally include amicroactuator that can deflect in response to applied stimuli, such aselectric fields, magnetic fields or thermal changes. For example,piezoelectric crystals undergo a strain when an electric field isapplied such that a deformation related to the magnitude of electricfield results. Suitable piezoelectric materials include, for example,quartz, barium titanate, lead zirconate-lead titanate andpolyvinylidenefluoride. Similarly, paramagnetic materials can be usedwhich can be designed to deflect in a magnetic field, such as from anelectromagnet. Thermal-based actuators can be formed from interfacesbetween materials with differences in coefficients of thermal expansion.

The polymer-inorganic particle blends can be incorporated into theactuator element and/or into an extension from the actuator withfunctional properties, such as desirable optical properties. Inparticular, an element comprising a polymer-inorganic particle blend canextend from a MEMS actuator, in which the element functions as a mirroror a lens. An actuator-based optical element can be incorporated intooptical devices, such as a tunable filter and or a tunable laser. Thesestructures are discussed further in the context of the followingfigures. With respect to incorporation into the actuator element itself,the polymer and/or the inorganic particles can be active with respect toactuator functionality. Specifically, the polymer and/or the inorganicparticles can be piezoelectric materials, paramagnetic materials ormaterials with a desired coefficient of thermal expansion. Similarly,the material can have desired optical properties for incorporation intoan optical device as a movable optical element.

A tunable vertical cavity surface-emitting laser (VCSEL) is shown inFIG. 11. Laser 190 includes a substrate 192 with a bottom mirror 194.Top mirror 196 is mounted on a membrane 198, which can be formed frompiezoelectric material. Membrane 198 is mounted on posts 200. Electrode202 is located along the top surface of substrate 192. Membrane 198 andelectrode 202 are connected to an appropriate power source 204 and avariable resistance 206. Membrane 198 and electrodes 202 form a portionof a MEMS device incorporated into the tunable laser. The distancebetween mirrors 194, 196 determines the frequency of the laser. Theposition of top mirror 196 is adjusted by providing a selective amountof current using variable resistance 206. Since membrane 198 is formedfrom piezoelectric material, membrane 198 deforms a particular amountaccording to the amount of current applied. A pump pulse can be suppliedthrough top mirror 196 into the laser cavity. The wavelength of thecorresponding emissions through bottom mirror 194 depends on theposition of top mirror 196. The lasing wavelengths for a mode m is givenby λ_(m)=2nL/m, where n is the index of refraction within the lasingcavity and L is the distance between the mirrors. The peak gain is alsoa function of the distance between the mirrors. The general structure ofVCSELs is described further, for example, in U.S. Pat. No. 6,160,830 toKiely et al., entitled “Semiconductor Laser Device And Method OfManufacture,” incorporated herein by reference.

In tunable vertical cavity surface-emitting laser 190, one or morecomponents can be formed from the polymer-inorganic particle blends. Inparticular, membrane 198 and/or top mirror 196 can be formed from blendsdescribed herein. The index-of-refraction of top mirror 196 can beselected to yield the desired optical properties. Furthermore, membrane198 can be formed from a polymer-inorganic particle blend in which thepolymer and/or the inorganic particles have piezoelectric propertiessuch that the application of current to the electrodes can result indeformation of membrane 198. Additionally or alternatively, one or moreother components of laser 190 can be formed from the blends.

Wavelength selective components are useful for performing wavelengthdivision multiplexing within networks to increase bandwidth. Suitabledispersive elements include, for example, diffraction gratings, prismsand the like. An arrayed waveguide grating is another wavelengthselective component of interest. An arrayed waveguide grating comprisestwo couplers and an array of waveguide channels, with one couple on eachside of the array of waveguide channels. The general principle ofarrayed waveguide gratings are described further in U.S. Pat. No.5,002,350 to Dragone, entitled “Optical Multiplexer/Demultiplexer,”incorporated herein by reference.

An embodiment of an arrayed waveguide grating is shown in FIG. 12.Arrayed waveguide grating 210 comprises couplers 212, 214 and an arrayof waveguides 216. Coupler 212 provides for coupling of an input signalinto array 216. At coupler 212, the waveguides of array 216 are stronglycoupled. Coupler 212 further is connected to input waveguides 218. Inone embodiment, coupler 212 can a physical broadening of the respectivewaveguide cores of both array 216 and input waveguides 218 and a gapbetween input waveguides 218 and array waveguides 216 with uniformindex-of-refraction such that signals are coupled from the geometry. Insome embodiments, coupler 212 includes broadened optical channels 220that lead to each waveguide of array 216.

Waveguide array 216 comprises a plurality of waveguides 226 withdifferent lengths from each other. The difference in lengths results ina phase shift in the light signals transmitted through the waveguides.The differences in lengths can be selected to result in a desiredinterference between light of particular wavelength at coupler 214. Theinterference at coupler 214 can result in a spatial separation of lightof different wavelengths. The different wavelength of light can bedirected to different spatially displaced output waveguides 224.

In particular, waveguides of array 216 are also strongly coupled atcoupler 214. Coupler 214 can include broadened optical channels 222 thatlead from waveguides of array 2116. Broadened optical channels 222 canbe arranged on an arc such that signals from each waveguide interfere.Coupler 214 can further include spatially displaced output waveguides224 with the spatial separation being responsible for a differentfrequency portion of the spectrum from the interfering signal from array216 transmitting through different output waveguides 224.

While the embodiment in FIG. 12 has five waveguides shown, other numbersof waveguides can be used. The number of waveguides and the differencein lengths of the waveguides generally determine the spectral resolutionof the wavelength split signal. Active elements can be incorporated intothe arrayed waveguide grating to tune the spectral decoupling. Forexample, an electroactive material and corresponding electrodes can beintroduced within one or more of the waveguides of array 216. The use ofactive elements within an arrayed waveguide grating is described furtherin U.S. Pat. No. 5,515,460 to Stone, entitled “Tunable Silicon BasedOptical Router,” incorporated herein by reference. One or more of theelements of the arrayed waveguide grating can comprise apolymer-inorganic particle blend. For example, the core of thewaveguides of waveguide array can be a polymer-inorganic particle blend.The index-of-refraction can be selected such that a convenient pathlength difference is introduced into the waveguide array.

Similarly, optical switches can be formed with polymer-inorganicparticle blends. A9 planar optical structure 230 with three opticalswitches 232 is shown in FIGS. 13 and 14. Fewer optical switches,additional optical switches and/or other integrated optical devices canbe incorporated into the structure, as desired. For convenience,cladding layers are not shown. Optical switches 232 include cores 234and switch elements 236. Switch elements 236 comprise apolymer-inorganic particle blend that is thermo-optical. As shown inFIG. 13, the temperature of a switch element 236 is set to adjust theindex-of-refraction of the polymer-inorganic particle blend such thatthe light in the waveguide is not transmitted and the switch is closed.Generally, the temperature of a switch element 236 can be selected toopen and close the switch to control light transmission through theswitch. As shown in FIG. 14, a thermal element 238, such as a resistiveheater or a cooling element, is placed near switch elements 236. Thermalelement 238 is used to control the temperature of adjacent switchelement 236 to open and close the switch by controlling theindex-of-refraction of switch element 236. The polymer-inorganicparticle blend within switch elements 236 can include polymer and/orinorganic particle that are thermo-optical. Some polymers have a largenegative change in index-of-refraction in response to an increase intemperature. Suitable polymers include, for example, halogenatedpolysiloxanes, polyacrylates, polyamides and polycarbonates. Suitablethermo-optical inorganic materials include, for example, quartz.

A cross-connect optical switch is shown in FIG. 15. As shown in FIG. 15,cross-connect optical switch 250 has two switch elements 252. Additionalswitch elements and/or integration with other optical devices can beincluded in the structure, as desired. Switch elements 250 can includethermo-optical, electro-optical or magneto-optical materials.Appropriate electrodes, electromagnets or thermal elements, asappropriate, can be properly placed adjacent switch elements 252 tocontrol the index-of-refraction of switch elements 250. A light pathstrikes switch elements 250 at an angle. The index-of-refraction of eachswitch element can be selected to transmit or reflect most of the lightas desired.

In some embodiments, structures have periodic formations incorporatingpolymer-inorganic blends, such as polymer-inorganic particle composites.The structure can have a periodicity in composition and/or property,such as an optical property, in one-dimension, two dimensions or threedimensions. Referring to FIG. 16, structure 254 has a substrate 256 withfour periodically spaced bars 258 of polymer-inorganic particle blends.For embodiments in which bars 258 are an optical material, periodicallyspaced bars 258 result in a periodic variation in index-of-refraction.Generally, bars 258 include the same materials such that they have thesame index-of-refraction as each other, although alternative embodimentsare described below. As shown in FIG. 16, air or other gas fills thespaces between bars 258 as a second material resulting in periodicinterfaces between the polymer-inorganic particle substrate and the gas.

In general, control of optical transmission is obtained by embeddingperiodic optical materials within a larger structure. Referring to FIG.17, a three-layered optical structure 260 is shown, in which hiddenstructure of the layers is shown with dashed lines. Structure 260includes a first layer 262, a second layer 264 and third layer 266.Second layer 264 includes periodically spaced sections of opticalmaterial 268 comprising a polymer-inorganic particle blend. Alternatingoptical material 270 is located between periodic sections 268. Opticalchannels 272, 274, which are outlined in dotted lines, extend in eitherdirection from the periodically spaced sections. Optical material 270may or may not be the same material as the optical material withinoptical channels 272, 274. Optical channels 272, 274 are orientedapproximately along the axis normal to the periodicity of sections 268.Optical channels 272, 274 can function as a waveguide or the like. Theindex-of-refraction of all of the materials can be selected based on thedesired function of periodic sections 268, 270 and optical channels 272,274.

Referring to FIG. 18, optical structure 280 has a two-dimensionalperiodic array 282 of alternating optical elements 284, 286. At least,optical elements 284 comprise a polymer-inorganic particle blend. Asshown in FIG. 18, another condensed-phase optical material 288, e.g.,surrounding core material, is located between around optical elements284, 286. In some embodiments, optical elements 286 and/or opticalmaterial 288 can be a gas. The optical material of elements 286 can bethe same as or different from optical material 288. In some embodimentsof interest, optical structure 280 can be embedded within a largersuperstructure with additional materials and or features, such asstructure 260 with three layers 262, 264, 266 and optical channel 270.Similarly, an optical structure 290 with three-dimensional periodicityis depicted in FIG. 19. Optical structure 290 has a three dimensionalperiodic array of optical elements 292, 294. At least optical elements292 comprise polymer-inorganic particle blends. Optical elements 294 arelocated between and around optical elements 292 such that a periodicvariation in index-of-refraction results in three dimensions. Opticalelements 294 can be formed from a polymer-inorganic particle blenddifferent from the material in optical elements 292 or from a differenttype of optical material. Optical elements 294 can be formed from thesame optical material as a surrounding optical material that integratesthe periodic optical structure into a larger optical structure in whichthe period optical structure 290 is embedded.

For convenience, the period structures in FIGS. 16–19 are depicted withthree or four elements in the periodic structure. In furtherembodiments, the number of elements in each dimension of the periodicstructure can be selected to obtain desired optical effects. The opticaleffect of the periodic structure generally depends on the opticalproperties of the material within the periodic structure and inparticular the difference in index-of-refraction at the interfacebetween the elements of the periodic structure. In particular, opticalproperties of the period structure depend on the index-of-refractiondifference between the periodic elements comprising a polymer-inorganicparticle material and the material between the elements comprising thepolymer-inorganic particle blend, although both of the alternatingoptical material in the periodic structure can comprisepolymer-inorganic particle blends with adjacent elements having adifferent composition and/or particle loading. In general, the periodicstructure has at least two elements in the period, in furtherembodiments at least about 3 elements in the period, in otherembodiments at least 5 elements in the period, in further embodimentsfrom 2 elements to about 1000 elements, in additional embodiments from10 elements to about 250 elements and in still other embodiments from 20elements to 100 elements. A person of ordinary skill in the art willrecognize that other ranges within these explicit ranges arecontemplated and are within the present disclosure. Generally, for someof the devices of interest, within a structure with periodic variationin index-of-refraction, having a greater difference inindex-of-refraction at optical interfaces results in a need for fewerperiodic elements in the structure to achieve a desired optical effect.The distance over which the period repeats generally is at least about10 nm, in further embodiments at least about 20 nm, in other embodimentsat least about 50 nm, in additional embodiments from about 20 nm toabout 10 microns and in other embodiments from about 50 nm to about 1micron. A person of ordinary skill in the art will recognize thatadditional ranges within these explicit ranges are contemplated and arewithin the present disclosure.

As depicted in FIGS. 16–19, the index-of-refraction varies in astep-wise fashion from one value to another value within the periodicstructure. However, by varying particle loadings and/or by usingdifferent composition of inorganic particles, a continuous or gradualstep-wise change in index-of-refraction can be achieved. Gradualstep-wise variation in index-of-refraction can have desirable opticalproperties relative to step-wise variation between upper and lowerlimits in index-of-refraction. Such versatility in index selection canbe used to approximate desired continuous functions ofindex-of-refraction as a function of distance, for example, by using aplurality of step-wise changes within the periodic structure. Inparticular, it may be desirable to have approximately a sinusoidalvariation in index-of-refraction. Such a structure is expected to giverise to a single reflection peak without the presence of any higherorder harmonics. A real space structure with a refractive index profilemade up of only a few (preferably a single) harmonic will result in areflection spectrum containing only a few (or preferably a single) peak.Tuning the amplitude and wavelength of the sinusoidal variation ofrefractive index influences the strength of the light's interaction withthe stack (structure) as well as the wavelength of the light interactingwith the stack, respectively.

Referring to FIG. 20, periodic structure 296 has a periodic change inindex-of-refraction with step-wise changes in index. The step-wisechanges approximate sinusoidal variation in index-of-refraction. Theperiodicity and the step-wise changes can be seen in the plot ofindex-of-refraction (n) as a function of distance “d” along thestructure in FIG. 21. The number of steps in each period and the numberof periods can be selected to achieve desired optical effects. Structure296 can be incorporated into larger superstructures as desired. Inaddition, similar step-wise variation in index-of-refraction can beintroduced within two-dimensional and three-dimensional periodicstructures.

Periodic variations in index-of-refraction within an optical structurecan be referred to as gratings (1-dimensional) or photonic crystals(1-dimensional, 2-dimensional or 3-dimensional). These devices can beused to form various optical devices. Thus, the ability to form theseperiodic variations in index-of-refraction provides a convenientapproach to the formation of integrated optical devices. Having anability to select the index-of-refraction differences provide increasedflexibility in device design. In particular, being able to form, usingconvenient processing approaches, interfaces with increased differencesin index-of-refraction allows for the formation of smaller devices.

Periodic index-variation in one-dimension can be used, for example, toform Bragg gratings that have various optical applications. Inparticular, Bragg gratings can be used, for example, to form opticalmirrors and optical band pass filters or interference filters. Ingeneral, when light transmitted through an optical material encounters achange in index-of-refraction, a portion of the light is transmitted anda portion of the light is reflected. If the variation inindex-of-refraction is periodic, the relative amounts of transmitted andreflected light depend on the difference in index-of-refraction, thenumber of periodic elements and the wavelength of light. Adjusting thedifference in index-of-refraction and the number of periodic elementscan be used to transmit and reflect desired portions of the spectrum.Mirrors reflect desired portions of the spectrum. The gratings can beincorporated into other structures such as lasers and the like.

Bragg gratings selectively transmit light wavelengths depending on thenumber of grating elements and the index-of-refraction differencesbetween the elements of the grating. Bragg gratings reflect somefrequencies while transmitting other frequencies. Polymer-inorganicparticle blends can be used for one or more components of the grating.By incorporating a blend with an index-of-refraction that depends onelectric field or temperature, the filter can be made tunable. Therelationships between transmission and reflection wavelengths as afunction of grating parameters are described further in U.S. Pat. No.6,278,817 to Dong, entitled “Asymmetric Low Dispersion Bragg GratingFilter,” incorporated herein by reference.

An embodiment of a tunable Bragg grating optical filter withpolymer-inorganic particle blends is shown in FIG. 22. Filter 310includes three layers 312 of polymer-inorganic particle blendinterspersed with a low index material 314. The polymer-inorganicparticle blend in layers 312 function as an electro-optical material inwhich the index-of-refraction varies with the application of an electricfield. Low index material 314 can be air, a low index polymer, a lowindex polymer-inorganic particle blend or other low index material. Atransparent substrate 316 can be used to support the filter, if desired.Spacers 318 can be used to separate layers 312 in some embodiments.Electrodes 320, 322 can be used to supply an electric field. Electrodes320, 322 are connected to power source 324, which can provide a variablevoltage to electrodes 320, 322 to provide desired tunability. Inparticular, the index-of-refraction of layers 312 vary with theapplication of an electric field while the filter function depends onthe index-of-refraction of layers 312. While the embodiment shown inFIG. 19 has three alternating index-of-refraction elements with high/lowindex, a greater number of elements in the grating can be used toachieve desired filtering properties. A greater index difference betweenthe high index and low index components of the grating results in a needfor fewer grating elements within the filter to obtain an equivalentresolution in the filtering.

With respect to polymer-inorganic particle blends in layers 312, thepolymer and/or the inorganic particles can have an index-of-refractionthat depends on electric field. Suitable electro-optical inorganicmaterials comprise, for example, lanthanum doped polycrystalline leadzirconate titanate, lithium niobate (LiNbO₃), KTaO₃, LiTaO₃, BaTiO₃,AgGaS₂, ZnGeP₂ and combinations thereof and doped compositions thereof.Suitable electro-optical polymers include, for example, polyamides withdissolved chromophores. Other electro-optical polymers are discussed inU.S. Pat. No. 6,091,879 to Chan et al., entitled “Organic PhotochromicCompositions And Method For Fabrication Of Polymer Waveguides,”incorporated herein by reference. Similar tunability is obtainable withthermo-optical materials within the polymer-inorganic particle blends ifthe materials are correspondingly thermally controlled.

Lasers can be formed from two Bragg gratings that form the partialmirrors OF the laser cavity. Pump beams drive the laser. Such Bragggrating lasers can be formed in optical fibers or as part of planaroptical structures. Lasers based on Bragg gratings are describedfurther, for example, in U.S. Pat. No. 5,237,576 to DiGiovanni et al.,entitled “Article Comprising An Optical Fiber Laser,” incorporatedherein by reference.

An embodiment of a laser formed with Bragg gratings is shown in FIG. 23.Laser 340 comprises an optical channel 342 with Bragg gratings 344, 346,amplification material 348 and secondary optical pathway 350. Opticalchannel 342 generally is a core surrounded by cladding in a fiber or ina planar structure. Bragg gratings 344, 346 have periodic variation inindex-of-refraction and can incorporate polymer-inorganic particleblends as described above. The characteristics of the gratings can beselected to reflect and transmit particular wavelengths for the laserfunction. Bragg gratings 344, 346 form the boundaries of a laser cavity352. The size of the laser cavity determines the modes/wavelengths ofthe laser emissions. Amplification material 348 is located within lasercavity 352. Amplifier material 348 is optically connected to secondaryoptical pathway 350. Amplifier material 348 includes materials thatabsorb light at an amplifier wavelength with a shorted wavelength thanthe wavelength of the laser. Generally, the amplifier wavelength is inthe ultraviolet. Suitable amplifier material includes, for example, rareearth doped amorphous particles. The production of rare earth dopedamorphous particles is described, for example, in copending and commonlyassigned Provisional Patent application 60/313,588 to Home et al.,entitled “Doped Glass Materials,” incorporated herein by reference.These particles can be incorporated into a polymer-inorganic particleblend.

A pump beam is directed into the laser through waveguide 342. The pumpbeam generally is in the visible or infrared portions of the spectrum. Aportion of the pump beam enters the laser cavity. An amplification beamis direct to amplification material 348 through secondary opticalpathway 350. The amplification beam can be supplied by an ultravioletlight source, such as an ultraviolet laser or a non-laser light source.Energy from the amplification beam is directed into the laser output bystimulated emission from the amplification material due to the pumpbeam.

Lattices with periodic variation in index-of-refraction in one-, two- orthree-dimensions are referred to as photonic band gap structures orphotonic crystals. Photonic crystals have been described as photonicanalogs of electronic semiconductors. Photonic crystals can provide afrequency gap covering a range of frequencies of electromagneticradiation that cannot propagate for any wavevector, i.e., in anydirection, including spontaneous emission. Light can be introduced intoa photonic crystal by applying light at an angle to the periodiclattice. The frequency gap depends on, for example, the unit cell size,the crystallographic orientation of the periodic structure, theindices-of-refraction including the differences in index betweendifferent materials of the lattice and other optical properties. Ingeneral, the differences in index-of-refraction between periodicmaterials of a photonic crystal are at least about 0.1 index units, inother embodiments, at least about 0.2 index units, in furtherembodiments, at least about 0.5 index units, in additional embodimentsfrom about 0.2 to about 2 index units and in some other embodiments fromabout 0.5 to about 1.5 index units. A person of ordinary skill in theart will recognize that additional ranges within these explicit rangesare contemplated and are within the present disclosure. In general, thedimensions of the photonic crystal lattice are on the same order ofmagnitude as the band gap wavelengths.

Defects can be introduced into the photonic crystal to provide forelectromagnetic propagation within the forbidden band gap. The defectsintroduce broken symmetry that interrupts the periodicity. Inparticular, defects can be variations in the periodic structure withrespect to size, location and/or optical properties of an element.Appropriate defects provide for selective propagation of wavelengths.Defects can result from processing limitations with respect totolerances of the processing approach or they can be purposelyintroduced. Thus, the photonic crystals with selected defects can beused as optical filters, switches, amplifiers, lasers and the like. Ingeneral, photonic crystals involve a difference in index-of-refractionof two or more index units. The evaluation of a photonic band gap for aone-dimensional photonic crystal is given in U.S. Pat. No. 6,002,522 toTodori et al., entitled “Optical Functional Element Comprising PhotonicCrystal,” incorporated herein by reference. The polymer-inorganicparticle blends can be incorporated into periodic optical structureswith large variations in index-of-refraction between the differentmaterials of the lattice. Periodic optical structures for formingphotonic crystals can be formed as described herein. Defects can beintroduced by varying the periodic structure. In particular, theperiodic structures described above can be used as photonic crystalswithin an optical structure if the differences in index-of- refractionare sufficient.

The periodic structures, e.g., photonic crystals, can be used in theformation of light absorbing structures, such as antenna and solarcells. In these structures, a light absorbing electron donor, such as aphotoconductive polymer, such as a doped polyphenylene vinylene can beplaced adjacent the polymer-inorganic particle blend that has acomposition to function as an electron accepting material. For example,the inorganic particles within the blend can be fullerenes, other carbonnanoparticles or semiconductive materials with electron holes foraccepting the electrons, such as micron sized silicon particles, asdescribed further in U.S. Pat. No. 5,413,226 to Matthews et al, entitled“Apparatus For Sorting Objects According To Size,” incorporated hereinby reference. Electrodes are placed around the electron donating andelectron accepting materials. If one surface is covered with anelectrode, the electrode can be a transparent electrode, for example,indium tin oxide. Solar cell structures are described further in U.S.Pat. No. 5,986,206 to Kambe et al., entitled “Solar Cells,” incorporateherein by reference.

In addition to periodic structures, optical structures can be formedwith polymer-inorganic particle blends that have quasi-periodic or quasicrystalline structures. Quasi-crystal structures can be quasi periodicin one-, two- or three- dimensions. Quasi periodic one-dimensionaloptical structures are described in U.S. Pat. No. 4,955,692 to Merlin etal., entitled “Quasi-Periodic Layered Structures,” incorporated hereinby reference. In these quasi periodic optical structures, layers of twodifferent optical materials with different indices-of-refraction can beordered according to a Fibonacci series with the following orderings, A;AB; ABA; ABAAB; ABAABABA; ABAABABAABAAB, etc. A and B indicateparticular optical layered structures. The Fourier spectrum can beevaluated for any of the resulting optical structures. For these andother quasi-periodic structures, the optical performance of an opticaldevice can be modeled using existing computer modeling techniques.

Processing of Composites Into Structures

The polymer-inorganic particle blends generally can be processed usingmethods developed for polymer processing. In selecting the processingapproaches for a blend, appropriate consideration can be given to thephysical properties of a particular blend as well as the desired form ofthe resulting structure. Relevant physical properties include, forexample, viscosity, solubility, flow temperatures and stability,although specific properties may only be relevant for certain processingapproaches. In particular, after the formation of a polymer-inorganicparticle blend, the blend can be further processed for storage and/orfor formation into desired structures. The additional processing of theblend following its formation may or may not take place in a solvent.The processing of polymer-inorganic particle composites may be differentfrom the processing approaches for polymer-inorganic particle mixtures.In particular, composites are more stable while the processing ofpolymer-inorganic particle mixtures may need to maintain thedistribution of particles within the polymer. The processing of thepolymer-inorganic particle blends can be coordinated with processingapproaches for other materials for the formation of interfaces and othercomponents of structures into which the polymer-inorganic particleblends are incorporated.

The blend can be molded, extruded, cast or otherwise processed usingpolymer processing technology to form various shapes of materials. Inaddition, the blend can be coated from a solvent-based slurry, spincoated or the like to form a coating of the composite. Any solvent canbe removed following the formation of a coating. Similarly, the blendcan be crosslinked following coating, whether or not asolvent/dispersant is used in the coating process. Thus, thesolidification process can involve solvent/dispersant removal and/orcrosslinking, such as thermal crosslinking, crosslinking withultraviolet light or an electron beam, or by adding a radical initiator.The coatings can be structured using mask techniques. In addition,self-assembly techniques can take advantage of the properties of thecomponents of the composite to assist with the formation of structureson a substrate, especially periodic structures, as described furtherbelow. To the extent that self-assembly is used, the self-assemblyprocess is combined with a localization approach that overlays atemplate as a boundary for the self-assembly approach.

Herein for convenience, the polymer-inorganic particle blend refers tothe bonded or unbonded inorganic particle and polymer/monomer materialwhether in solution, a dispersion, a melt, a coating or a solid form.For example, the properties of a solution/dispersion, such asconcentration and solvent composition, containing the polymer-inorganicparticle blend can be modified to facilitate the further processing, forstorage of the composite and/or for forming structures.Solutions/dispersions that are more dilute generally have a lowerviscosity. In some processing approaches, the polymer-inorganic particlecomposite is processed as a melt.

The solution/dispersion in which the composite is formed can be useddirectly for further processing. Alternatively, the composite can beremoved from the liquid or placed in a different liquid. The liquid ofthe solution/dispersion can be changed by dilution, i.e., the additionof a different liquid to solution/dispersion, by dialysis to replace theliquid if the composite has sufficient molecular weight to be retainedby dialysis tubing, or by removing the liquid andsolubilizing/dispersing the composite with the replacement liquid.Dialysis tubings with various pore sizes are commercially available. Tosubstitute liquids, a liquid mixture can be formed, and subsequently theoriginal liquid is removed by evaporation, which can be particularlyeffective if the liquids form an azeotrope. The polymer/inorganiccomposite can be removed from a liquid by evaporating the liquid, byseparating a dispersion of the complex by filtration or centrifugation,or by changing the properties, such as pH, liquid composition or ionicstrength, of the solution/dispersion to induce the settling of thecomplex from the liquid.

Generally, the composite can be processed using standard polymerprocessing techniques, including heat processing and solvent processingapproaches. For example, the polymer/inorganic particle composite can beformed into structures by compression molding, injection molding,extrusion and calendering. In other words, the composites can be formedinto free structures, such as sheets. Similarly, the composites can beformed into fibers or a layer on a fiber using techniques, such asextrusion or drawing a softened form of the composite.Solutions/dispersions can be formed into films/coatings by spin castingand similar methods. Coatings can be formed with various parametersincluding, for examples, thin coatings with thicknesses less than about1 micron.

To form structures from the polymer-inorganic particle blends,generally, the blends are processed along with one or more additionalmaterials to form appropriate interfaces within the structures based ondesired function. The processing of the polymer-inorganic particleblends can further depend on the properties of associated materialswithin the structures. Depending on the desired structure, thepolymer-inorganic particle blends may or may not be localized withindomains within a layer or other extent of the structure.

For the formation of structures from the polymer-inorganic particleblends, the blends can be selectively deposited over appropriate regionsor the blends can be selectively removed to leave the desired structure.To selectively deposit the blend, the blends can be deposited, forexample, using print technology or using a template. With respect toprinting the blend, ink jet technology can be adapted for the printingof the blends in an appropriate solvent/dispersant along desiredpatterns.

With respect to template technology, standard lithographic approachesusing photoresist masks can be adapted for deposition of the blends. Forexample, the blends can be deposited between gaps in the photoresist.Excess blend outside of the gaps can be removed along with thephotoresist. Similarly, sacrifice layers can be used. Sacrifice layers,like photoresist materials, are selectively etched, for example, using achemical compound, that selectively removes the sacrifice layer after ithas functioned as a template. Alternatively, a physical mask can beused. A physical mask has a separate structure apart from the surface,in contrast with sacrifice layers and photoresist layers that areintegral with the surface being contoured. Physical masks can bephysically removed after the masking process is complete and, in someembodiments, can be reused. Physical masks can be etched or cut, forexample, with a laser, from a ceramic material or a metal.

Similarly, a coating of polymer-inorganic particle blends can bedeposited, and a selected portion of the blend can be removed to form apattern. For, example, etching, such as dry etching, can be used toselectively remove the blend. Reactive ion etching, such as reactiveoxygen etching, generally is appropriate for the removal ofpolymer-inorganic particle blends. Lithographic techniques, such asphotolithography with photoresist, can be used to shield portions of theblend during the etching process. Alternatively, a focused ion orradiation beam can be used to perform the etching without the need for amask.

To form periodic structures, the polymer-inorganic particle blends canbe deposited using the above noted patterning approaches with a periodicpattern. Alternatively, a period pattern can be formed by takingadvantage of self-assembly approaches to facilitate the assemblyprocess. Self-assembly processes take advantage of natural ordering dueto molecular ordering and/or molecular recognition. Thepolymer-inorganic particle blends can exhibit self-organizationproperties that can be exploited in self-assembly processes.

In particular, to facilitate formation into localized devices, polymerscan be selected for self-organization properties that assist theself-assembly. The self-organization properties can be associated withfeatures of a copolymer or from a physical polymer blend. Based on thesepotential self-organization properties of the polymers, apolymer-inorganic particle blend can incorporate self-assembly to forminto a localized structure. Self-assembled structures can be formed fromself-assembly with particles segregated to one or another phase of thepolymer within the blend, in which different polymer phases areidentifiable due to self-organization. In particular, some self-assemblyoperations naturally form periodic structures that can be used informing periodic variations in index-of-refraction.

In addition, the formation of localized structures also involvesformation of boundaries for the structures. Generally, the self-assemblyprocess forms an ordered network while a localization process forms theboundaries of the self-assembly process. Thus, periodic structures canbe formed with the self-assembly process imposing the periodicity whilea separate localization process forms the boundary of the periodicstructure.

As an example, ordered polymers have properties that can promote naturalsegragation that can be exploited within a self-assembly framework.Ordered polymers include, for example, block copolymers. Blockcopolymers can be used such that the different blocks of the polymersegregate, which is a standard property of many block copolymers. Otherordered copolymers include, for example, graft copolymers, combcopolymers, star-block copolymers, dendrimers, mixtures thereof and thelike. Ordered copolymers of all types can be considered a polymer blendin which the polymer constituents we chemically bonded to each other.Physical polymer blends may also be used as ordered polymer and may alsoexhibit self-organization, as described further in copending andcommonly assigned U.S. patent application Ser. No. 09/318,141, now U.S.Pat. No. 6,599,631 to Kambe et al., entitled “Polymer-Inorganic ParticleComposites.” incorporated herein by reference. Physical polymer blendsinvolve mixtures of chemically distinct polymers.

Using ordered copolymers, a portion of the polymer-inorganic particleblend can have a significantly different index-of-refraction thananother portion of the blend. Using self-assembly techniques, theportions of the blend with different indices-of-refraction can beordered to form a physical interface between the materials with thedifferent indices-of-refraction. Furthermore, periodic structures can beused to form periodic variation in the index-of-refraction.Specifically, periodicity of the index-of-refraction can be created inmore than one dimension. The one-dimensional and multidimensionalvariation in index-of-refraction can be advantageously used to formphotonic crystals.

Suitable block copolymers for self-organization include, for example,polystyrene-block-poly(methyl methacrylate),polystyrene-block-polyacrylamide, polysiloxane-block-polyacrylate,suitable mixtures thereof and the like. These block copolymers can bemodified to include appropriate functional groups to bond with thelinkers. For example and without limitation, polyacrylates can behydrolyzed or partly hydrolyzed to form carboxylic acid groups, oracrylic acid moieties can be substituted for all or part of theacrylated during polymer formation if the acid groups do not interferewith the polymerization. Alternatively, the ester groups in theacrylates can be substituted with ester bonds to diols or amide bondswith diamines such that one of the functional groups remains for bondingwith a linker. Block copolymers with other numbers of blocks and othertypes of polymer compositions can be used.

The inorganic particles can be associated with only one of the polymercompositions within the block such that the inorganic particles aresegregated together with that polymer composition within the segregationblock copolymer. For example, an AB di-block copolymer can includeinorganic particles only within block A. Segregation of the inorganicparticles can have functional advantages with respect to takingadvantage of the properties of the inorganic particles. Similarly,tethered inorganic particles can separate relative to the polymer byanalogy to different blocks of a block copolymer if the inorganicparticles and the corresponding polymers have different solvationproperties. In addition, the nanoparticles themselves can segregaterelative to the polymer to form a self-organized structure.

Polymer blends involve mixtures of chemically distinct polymers. Theinorganic particles may bond to only a subset of the polymer species, asdescribed above for block copolymers. Physical polymer blends canexhibit self-organization similar to block copolymers. The presence ofthe inorganic particles can sufficiently modify the properties of thecomposite that the interaction of the polymer with inorganic particlesinteracts physically with the other polymer species differently than thenative polymer alone. Even with a single polymer, if the particles arenot uniformly distributed within the polymer, the polymer with higherparticle loadings can separate from the polymer portions with lowerparticle loadings to form a self-assembled structure.

Regardless of the self-organization mechanism, some self-organizedpolymer-inorganic particle blends involve particle, such asnanoparticles, aligned with periodicity in a superstructure or supercrystal structure. The particles may or may not be crystallinethemselves yet they will exhibit properties due to the ordered structureof the particles. Photonic crystals make use of these crystalsuperstructures, as described further below.

The self-organization capabilities of a polymer-inorganic particle blendcan be used advantageously in the formation of self-assembled structureson a substrate surface. To bind the composite to the surface, thepolymer can be simply coated onto the surface or the composite can formchemical bonds with the surface. For example and without limitation, thepolymer can include additional functional groups that bond to one ormore structures and/or one or more materials on the surface. Theseadditional functional groups can be functional side groups selected toassist with the self-assembly process.

Alternatively, the substrate surface can have compositions, a surfacelinker, that bond to the polymer and/or to the inorganic particles suchthat a composite is bonded to the surface through the polymer or theinorganic particles. For example, the substrate can include organiccompositions with one or more functional groups such as halogens, suchas Br, CN, SCOCH₃, SCN, COOMe, OH, COOH, SO₃, COOCF₃, olefinic sites,such as vinyl, amines, thiol, phosphonates and suitable combinations ofany two or more thereof. In other embodiments, the surface linker hasfunctional groups that react with unreacted functional groups in thepolymer. Appropriate functional groups in the surface linker to bondwith the polymer can be equivalent to the functional groups in thecomposite linker to bond with the polymer.

In some embodiments involving self-assembly with particles, such asnanoparticles, a portion of the substrate surface is provided withpores, which can be holes, depressions, cavities or the like. The porescan be in an ordered array or a random arrangement. The size of thepores should be larger than the size of the nanoparticles. Generally,the pores have a diameter less than a micron, although the preferredsize of the pores and density of the pores may depend on the particulardesired properties of the resulting device. In addition, the spacingbetween pores can be controlled to be on the order of microns orsubmicron scales.

To deposit a polymer-inorganic particle blend within the pores, thesurface is contacted with a dispersion of the blend. Then, for example,the dispersion is destabilized with respect to the blend, such that theblend tends to settle onto the surface and into the pores. Thedispersion can be destabilized by altering the pH, such as adjusting thepH toward the isoelectric point, by diluting surfactants or by adding acosolvent that results in a less stabile dispersion. The dispersion isremoved after the deposition of a desirable amount of the blend. Then,blend on the surface not in the pores can be removed. For example, thesurface can be rinsed gently with a dispersant to remove composite onthe surface. Alternatively, the surface can be planarized by polishing,such as mechanical polishing or chemical-mechanical polishing. If thedispersant is properly selected to be not too effective at dispersingthe blend and if the rinsing is not done too extensively, the blendalong the surface can be preferentially removed while leaving the blendwithin the pores behind.

A porous structure can be formed using anodized aluminum oxide or othermetal oxides. Anodized aluminum oxide forms highly oriented and veryuniform pores. Pores are formed in anodic aluminum oxide by place analuminum anode in a solution of dilute acid, such as sulfuric acid,phosphoric acid, or oxalic acid. As the aluminum is oxidized, aluminumoxide with pores is formed. Pore diameters at least can be variedbetween 4 nm and 200 nm. The pores have a depth on a micron scale. Theformation of porous anodized aluminum oxide is described, for example,in D. Al-Mawlawi et al., “Nano-wires formed in anodic oxidenanotemplates,” J. Materials Research, 9:1014–1018 (1994) and D.Al-Mawlawi et al., “Electrochemical fabrication of metal andsemiconductor nano-wire arrays,” in Proc. Symp. Nanostructured Mater.Electrochem., 187th Meeting Electrochem. Soc., Reno, Nev., May 21–26,1995, Electrochem. Soc. 95 (8):262–273 (1995), both of which areincorporated herein by reference. The use of block co-polymers to formordered array of pores from silica and filling the pores to form aphotonic crystal is described in U.S. Pat. No. 6,139,626 to Norris etal., entitled “Three-Dimensionally Patterned Materials and Methods ForManufacturing Same Using Nanocrystals,” incorporated herein byreference.

The formation of a plurality of devices on a surface requires thelocalization of compositions active in the devices within prescribedboundaries associated with the particular device. To localize astructure within prescribed boundaries by self-assembly, the overallprocedure generally requires both a process defining the boundaries ofthe structure and a separate self-assembly process using a chemicalaffinity to associate the compositions of the device within theboundaries. The boundary defining process generally utilizes externalforces to define the extent of the structures. The self-assembly processitself generally does not define the boundaries of the structure.Self-assembly is based on a natural sensing function of thecompositions/materials that results in a natural ordering within theresulting structure as the compositions/materials associate. In general,the localization step can be performed before or after the self-assemblyprocess, although the nature of the processing steps may dictate aparticular order. The net effect results in a self-assembled structurewith a corresponding coverage of polymer/inorganic particle compositewithin the boundary and an area outside of the boundary lacking thiscoverage.

The separate boundary defining process is coupled to the self-assemblyprocess by activating the self-assembly process within the boundaries orby deactivating the area outside of the boundaries. Generally, anoutside force is applied to perform the activation or deactivationprocess. The localization can be performed, for example, using a mask orthe like, or using maskless lithography with focused radiation, such asan electron beam, an ion beam or a light beam.

The identification of a suitable activation or deactivation techniquemay depend on the particular self-assembly approach used. Thelocalization approaches generally involve either activation of the areafor the placement of the self-assembled structure or by deactivatinglocations separate from the selected locations. In particular, thelocalization approach isolates the region for the formation of theself-assembled structure. Suitable physical forces or chemical materialsare applied to perform the activation/deactivation.

Various approaches can be adapted for these purposes, including, forexample, conventional integrated electronic circuit processingapproaches. Specifically, mask techniques can be used to isolate theboundaries of the activation/deactivation process. Radiation or chemicalapplication can be performed in regions defined by the mask. Similarly,focused beams can be used to perform the localization. Suitable focusedbeams to achieve surface modification include, for example, light beams,such as ultraviolet light or x-ray, laser beams, electron beams or ionbeams, which can be focused to impinge on the selected region to performactivation or deactivation. Suitable focusing approaches are known inthe art.

An activation process can involve the formation of a specific materialat the desired location or the removal of a material or composition thatis inhibiting self-assembly at the desired location. Specifically, aparticular material can be formed within the boundaries that allows forthe self-assembly process to occur within the boundaries, while thesurface material outside of the boundaries does not allow for theself-assembly process. For example, a chemically reactive layer can beformed within the boundaries that bind to a polymer, while the substratesurface outside the boundary has a different chemical functionality thatdoes not bind to the polymer. Similarly, a layer of an inhibitingcompound can be removed from the area within the boundaries to expose asurface material that binds to a compound required in the self-assemblyprocess, such as a surface linker. The inhibiting compound can be aphotoresist compound in some instances that physically blocks thesurface and is selectively removable before or after the self-assemblyprocess. The composition of the photoresist or other inhibition compoundis selected to inhibit the self-assembly process such that the regionscovered by the inhibitory compound surrounding the boundary regionsubsequently do not become involved in the self-assembly process.

Similarly, the regions outside of the boundary region can bedeactivated. For example, a composition that binds a compound involvedin the self-assembly process can be applied over an entire surface.Then, the composition can be removed from outside of the bounded regionselected for the self-assembly process. Then, the self-assembly processonly takes place within the bounded region. In addition, an inhibitormaterial can be specifically deposited outside of the boundary region sothat the self-assembly process only takes place within the boundedregion where the inhibitory material has been removed. Similarly,radiation can be used to inactivate or dissociate compounds outside ofthe bounded region. The mask and/or focused beam approaches describedabove can be used to perform the deactivation processes. As noted above,strata or layers can be processed to produce a three-dimensionalintegrated structure.

A localization process used along with self-assembly is describedfurther in copending and commonly assigned U.S. patent application Ser.No. 09/558,266, now U.S. Pat. No. 6,890,624 to Kambe et at., entitled“Self Assembled Structures,” incorporated herein by reference.

EXAMPLES Example 1

Formation of Titanium Oxide Particles

Rutile TiO₂, anatase TiO₂, and oxygen deficient blue TiO₂ particles wereproduced by laser pyrolysis. The reaction was carried out in a chambercomparable to the chamber shown in FIGS. 24–26.

Referring to FIGS. 24–26, a pyrolysis reaction system 400 includesreaction chamber 402, a particle collection system 404 and laser 406.Reaction chamber 402 includes reactant inlet 414 at the bottom ofreaction chamber 402 where reactant delivery system 408 connects withreaction chamber 402. In this embodiment, the reactants are deliveredfrom the bottom of the reaction chamber while the products are collectedfrom the top of the reaction chamber.

Shielding gas conduits 416 are located on the front and back of reactantinlet 414. Inert gas is delivered to shielding gas conduits 416 throughports 418. The shielding gas conduits direct shielding gas along thewalls of reaction chamber 402 to inhibit association of reactant gasesor products with the walls.

Reaction chamber 402 is elongated along one dimension denoted in FIG. 24by “w”. A laser beam path 420 enters the reaction chamber through awindow 422 displaced along a tube 424 from the main chamber 426 andtraverses the elongated direction of reaction chamber 402. The laserbeam passes through tube 428 and exits window 430. In one preferredembodiment, tubes 424 and 428 displace windows 422 and 430 about 11inches from the main chamber. The laser beam terminates at beam dump432. In operation, the laser beam intersects a reactant stream generatedthrough reactant inlet 414.

The top of main chamber 426 opens into particle collection system 404.Particle collection system 404 includes outlet duct 434 connected to thetop of main chamber 426 to receive the flow from main chamber 426.Outlet duct 434 carries the product particles out of the plane of thereactant stream to a cylindrical filter 436. Filter 436 has a cap 438 onone end. The other end of filter 436 is fastened to disc 440. Vent 442is secured to the center of disc 440 to provide access to the center offilter 436. Vent 442 is attached by way of ducts to a pump. Thus,product particles are trapped on filter 436 by the flow from thereaction chamber 402 to the pump.

Titanium tetrachloride (Strem Chemical, Inc., Newburyport, Mass.)precursor vapor was carried into the reaction chamber by bubbling Ar gasthrough TiCl₄ liquid in a container at room temperature. C₂H₄ gas wasused as a laser absorbing gas, and argon was used as an inert gas. O₂was used as the oxygen source. Additional argon was added as an inertdiluent gas. The reactant gas mixture containing TiCl₄, Ar, O₂ and C₂H₄was introduced into the reactant gas nozzle for injection into thereactant chamber.

Representative reaction conditions for the production of rutile TiO₂particles and anatase TiO₂ particles are described in Table 1. Theblue-oxygen deficient rutile TiO₂ (TiO₂-2) was obtained from the sameconditions as the rutile TiO₂ particles (TiO₂-1) in Table 1, except thatthey were collected closer to the reaction zone by positioning theparticle collector accordingly. Low chamber pressure and low partialpressure of oxygen contribute to the oxygen deficiency in the resultingTiO₂. Heating of the particles slightly in air results in the loss ofblue color and the formation of a rutile structure. The reason for thecolor difference is not solely due to level of oxygen content, andcurrently is not completely understood.

TABLE 1 TiO₂-1 TiO₂-3 Phase Rutile TiO₂ Anatase TiO₂ BET Surface Area(m²/g) 64 57 Pressure (Torr) 110 150 Ar-Dilution Gas (slm) 4.2 8.4Ar-Win (slm) 10.0 10.0 Ar-Sld. (slm) 2.8 2.8 Ethylene (slm) 1.62 1.25Carrier Gas - Ar (slm) 0.72 0.72 Oxygen (slm) 2.44 4.5 Laser Power -Input 1400 1507 (Watts) LaserPower - Out (watts) 1230 1350 sccm =standard cubic centimeters per minute slm = standard liters per minuteArgon-Win. = argon flow through inlets 490, 492 Argon-Sld. = argon flowthrough slots 554, 556

An x-ray diffractogram of product nanoparticles produced under theconditions in Table 1 are shown in FIG. 27. Sample TiO₂-1 had an x-raydiffractogram corresponding to rutile TiO₂. Sample TiO₂-2 had an x-raydiffractogram similar to sample TiO₂-1. Sample TiO₂-3 had an x-raydiffractogram corresponding to anatase TiO₂. The broadness of the peaksin FIG. 27 indicates that sample 1 is less crystalline than the othertwo samples. Some peaks in the spectra of sample TiO₂-1 seem tooriginate from amorphous phases. Mixed phase particles can also beproduced. FIG. 28 represents a typical transmission electron micrograph(TEM) of the particles. The average particle size φ_(av) is around 10–20nm. There are effectively no particles beyond 2φ_(av).

Optical absorption spectra were obtained for titanium oxide particles inethanol at a concentration of 0.003 weight percent. The spectra for theTiO₃-3 sample is shown in FIG. 29. For comparison, similar spectra wereobtained for a commercial TiO₂ powders dispersed in ethanol at aconcentration of 0.0003 weight percent, which is shown in FIG. 30. Thesecond commercial powder was obtained from Aldrich Chemical Company,Milwaukee, Wis., and had an average particle size of 0.26 microns.

The absorption spectrum of the TiO₂ in FIG. 30 is exemplary of bulk TiO₂with a large absorption in the visible and infrared portions of thespectra. In contrast, the absorption spectrum of the powders in FIG. 29has a very reduced absorption in the visible and infrared portions ofthe spectra and enhanced absorption in the ultraviolet. This shift andnarrowing of the absorption spectra is due to the reduced size of theparticles.

Example 2

Nano-Polymer Composites

The formation of composites with poly(acrylic acid) and TiO₂-3 powderswith silane based linkers is described in this example.

The particles were well suspended in ethanol. Most of the particlesremained suspended after 2 weeks. High level of particle dispersion wasachieved, which was found significant for developing optical qualitynanocomposites. Secondary particle size in the suspensions wereevaluated with a Horiba Particle Size Analyzer (Horiba, Kyoto, Japan).Analysis with the particle size analyzer showed good dispersion/lowagglomeration.

Surface treatment of the three types of TiO₂ particles was performedwith aminopropyl triethoxy silane (APTES) as a silylation reagent. APTESis thought to bond to the particles by the following reaction:Particle-Ti—OH+((CH₃CH₂O)₃—SiCH₂CH₂CH₂NH₂→Particle-Ti—O—Si(OCH₂CH₃)₂CH₂CH₂CH₂NH₂Further successive hydrolysis of the ethoxy groups can form additionalSi bonds to the particle through ether-type linkages. Someself-polymerization of the silylation reagent can take place also,especially if excess silylation reagent and water are present.Well-suspended APTES coated TiO₂-3 particles were prepared using ethanolas a solvent/dispersant.

Polyacrylic acid was added to the functionalized particles. Generally,the polyacrylic acid had an average molecule weight of 250,000 Daltons,although some samples were prepared with low molecular weight polymerhaving an average molecular weight of 2,000 Daltons. The polyacrylicacid is thought to react with by way of the carboxylic acid group withthe primary amine of the silylation agent to form an amide bond. Thefirst interaction of the polymer with the surface treated particlesinvolves the salt formation of the carboxylic acid with the primaryamine. Then, at temperatures of 140 °–160° the salt units condense toform amide bonds. This reaction is depicted schematically as follows:Polymer-COOH+H₂N— . . . —Si—O—Ti-particle→Polymer-CONH— . . .Si—O—Ti-particle.A fourier transform infrared spectrum of the composite had an infraredabsorption band at 1664 cm⁻¹, which is a frequency characteristic of anamide bond. Scanning electron microscopy (SEM) images confirm thesuccessful synthesis of TiO₂-PAA nanocomposites. Also, the compositesformed from the functionalized particles exhibited significantly higherthermal stability than corresponding poly-inorganic particle mixtures.

Coatings were formed of the resulting composite by placing drops on asurface. The drops spread on the surface and were allowed to dry. Thedried composites were further analyzed. In particular, much smoothermaterials were formed from the functionalized particles(polymer-inorganic particle composites) than with the unfunctionalizedparticles (polymer-inorganic particle mixtures).

Example 3

Optical Measurements On PAA-Titania Composites

For the composites formed with polyacrylic acid and titania particles,index-of-refraction as a function of particle loading and optical losswere evaluated.

Refractive index measurements were performed using a Gaertner modelL-16C ellipsometer operating at 632.8 nm. Samples with different levelsof nanoparticle doping were coated on silicon wafers. Refractive indexmeasurements were performed at incidence angles of 50 and 70 degrees.

FIG. 31 illustrates evidence of index control that can cover asubstantial range based on selection of constituents and particleloadings for polymer-inorganic particle blends, especially composites.Solely by varying a loading level of TiO₂ nanoparticles (n₁˜2.6–2.9depending on anatase or rutile) in a PAA host (n₂˜1.48), the index canbe controlled by a factor of over 150% with respect to that of the PAAhost. All index values are reference to light at 632.8 nm. Appropriateselection of nanoparticles (high index) and polymer host is expected toincrease the controllable range of the index.

Optical extinction measurements were performed using a Hewlett Packardmodel 8452A spectrophotometer. Samples were suspended in ethanol orprepared as films on fused silica substrates. Measurements wereperformed in a fused silica cuvette with an optical path length of 1 cm.Low optical loss was maintained over a wide range of particle loadings.Even at a 50 weight percent particle loading, the composites were foundto have high levels of transparency in the visible and infrared portionsof the spectrum. This observation is very significant with respect toapplication of the composites as a building block for optical networkcomponents.

FIGS. 29 and 30, respectively, show optical absorption spectra fornano-TiO₂ (φ_(av)˜20 nm) and commercial TiO₂ particles (φ_(av)˜700 nm)both at a concentration of 0.003 % by weight in ethanol. The latterscatters visible light far more than the nanoparticles, thereby yieldinga higher level of optical attenuation. In addition, nano-TiO₂ shows asignificant increase in the ultraviolet (UV) light absorption that isconsidered as a quantum-size effect. This shift in absorption spectrumcan be used advantageously in optical materials for transmitting visibleor infrared light.

This example demonstrates a capability to control the refractive indexof nanoparticles-polymer composites through adjustment of the particleloading. Use of prefromed nanoparticles enables a large index contrastbetween adjacent materials through adjustment of particle loadings,although other materials changes can also be used to establish a largeindex contrast at an interface with a polymer-inorganic particle blend.A high level of uniformity in nanoparticles as well as excellentdispersion and appropriate surface modification over nanoparticles areuseful for the successful synthesis of photonic polymer-inorganicparticle blends, such as nanocomposites.

As utilized herein, the term “in the range(s)” or “between” comprisesthe range defined by the values listed after the term “in the range(s)”or “between”, as well as any and all subranges contained within suchrange, where each such subrange is defined as having as a first endpointany value in such range, and as a second endpoint any value in suchrange that is greater than the first endpoint and that is in such range.

The embodiments described above are intended to be illustrative and notlimiting. Additional embodiments are within the claims below. Althoughthe present invention has been described with reference to specificembodiments, workers skilled in the art will recognize that changes maybe made in form and detail without departing from the spirit and scopeof the invention.

1. An optical structure comprising a first optical material and a secondoptical material each of which comprises a polymer with the firstoptical material having an interface with the second optical material,the first optical material comprising a polymer-inorganic particle blendand the second optical material comprising a polymer-inorganic particleblend, wherein the blend comprises inorganic particles and wherein thefirst optical material has a different index-of-refraction than thesecond optical material at infrared, visible or ultraviolet wavelengthsand wherein the index-of-refraction of the first optical material variesspatially due to changes in the particle loadings, changes in inorganicparticle composition or both.
 2. The optical structure of claim 1wherein the two materials differ in values of index-of-refractionbetween each other by at least about 0.005 at infrared, visible orultraviolet wavelengths.
 3. The optical structure of claim 1 wherein thetwo materials differ in values of index-of-refraction between each otherby at least about 0.1 at infrared, visible or ultraviolet wavelengths.4. An optical structure comprising a first optical material and a secondoptical material each of which comprises a polymer with the firstoptical material having an interface with the second optical material,the first optical material comprising a polymer-inorganic particle blendand the second optical material comprising a polymer-inorganic particleblend, wherein the blend comprises inorganic particles, wherein thefirst optical material has a different index-of-refraction than thesecond optical material at infrared, visible or ultraviolet wavelengthsand wherein the polymer-inorganic particle blend has a non-liner opticalresponse at infrared, visible or ultraviolet wavelengths.
 5. The opticalstructure of claim 1 wherein the polymer-inorganic particle blendcomprises a polymer-inorganic particle mixture.
 6. The optical structureof claim 1 wherein the polymer-inorganic particle blend comprises apolymer-inorganic particle composite.
 7. The optical structure of claim1 wherein the polymer inorganic-particle blend comprises inorganicparticles comprising elemental metal or elemental metalloid, i,e,un-ionized elements, metal/metalloid oxides, metal/metalloid nitrides,metal/metalloid carbides, metal/metalloid sulfides or combinationsthereof.
 8. The optical structure of claim 1 wherein the polymerinorganic-particle blend comprises a polymer selected from the groupconsisting of polyamides (nylons), polyimides, polycarbonates,polyurethanes, polyacrylonitrile, polyacrylic acid, polyacrylates,polyacrylamides, polyvinyl alcohol, polyvinyl chloride heterocyclicpolymers, polyesters, modified polyolefins, polysilanes, polysiloxane(silicone) polymers, and copolymers and mixtures thereof.
 9. The opticalstructure of claim 1 wherein the second optical material comprises nomore than about 5 weight percent inorganic particles.
 10. The opticalstructure of claim 1 wherein the second optical material comprises atleast about 10 weight percent inorganic particles.
 11. The opticalstructure of claim 1 wherein the first optical material comprises atleast about 10 weight percent inorganic particles.
 12. The opticalstructure of claim 1 wherein the first optical material comprises atleast about 25 weight percent inorganic particles.
 13. The opticalstructure of claim 1 wherein the inorganic particles have an averageparticle size of no more than about 1 micron.
 14. The optical structureof claim 1 wherein the inorganic particles comprises metal/metalloidoxide particles.
 15. The optical structure of claim 1 wherein the blendcomprises inorganic particles and wherein the inorganic particles havean average particle size of no more than about 1 micron and whereinessentially no inorganic particles have a diameter greater than aboutfive times the average particle diameter and wherein the inorganicparticles comprise metal oxide.
 16. The structure of claim 15 whereinthe inorganic particles are electrically conducting.
 17. The structureof claim 4 wherein the inorganic particles have an average particle sizeof no more than about 500 nm.
 18. The structure of claim 4 wherein theinorganic particles have an average particle size of no more than about100 nm.
 19. A structure comprising a first material and a secondmaterial each of which comprises a polymer with the first materialhaving an interface with the second material, the first materialcomprising a polymer-inorganic particle blend, wherein the blendcomprises inorganic particles comprising metal nitride or metalloidnitride and wherein the inorganic particles have an average particlesize of no more than about 1 micron.
 20. A structure comprising a firstmaterial and a second material each of which comprises a polymer withthe first material having an interface with the second material, thefirst material comprising a polymer-inorganic particle blend, whereinthe blend comprises inorganic particles comprising a metal/metalloidcompounds with a dopant and wherein the inorganic particles have anaverage particle size of no more than about 1 micron.
 21. The structureof claim 19 wherein the first material and the second material areoptical materials and wherein the two materials differ in values ofindex-of-refraction between each other by at least about 0.005 atinfrared, visible or ultraviolet wavelengths.
 22. The structure of claim19 wherein the first material and the second material are opticalmaterials and wherein the two materials differ in values ofindex-of-refraction between each other by at least about 0.1 atinfrared, visible or ultraviolet wavelengths.
 23. The structure of claim19 wherein the polymer-inorganic particle blend has a non-linear opticalresponse at infrared, visible or ultraviolet wavelengths.
 24. Thestructure of claim 19 wherein the particle-inorganic particle blendcomprises a polymer-inorganic particle mixture.
 25. The structure ofclaim 19 wherein the particle-inorganic particle blend comprises apolymer-inorganic particle composite.
 26. The structure of claim 19wherein the second material comprises a polymer-inorganic particleblend.
 27. The structure of claim 19 wherein the first materialcomprises at least about 10 weight percent inorganic particles.
 28. Thestructure of claim 19 wherein the inorganic particles comprise a metalnitride.
 29. The structure of claim 19 wherein the inorganic particlescomprise silicon nitride.
 30. The structure of claim 19 whereinessentially no inorganic particles have a particle diameter greater thanabout four times the average particle diameter.
 31. The structure ofclaim 19 wherein the inorganic particles have a distribution ofdiameters with at least about 95 percent of the primary particles havinga diameter greater than about 60 percent of the average diameter andless than about 140 percent of the average diameter.
 32. The structureof claim 19 wherein the polymer inorganic-particle blend comprises apolymer selected from the group consisting of polyamides (nylons),polyimides, polycarbonates, polyurethanes, polyacrylonitrile,polyacrylic acid, polyacrylates, polyacrylamides, polyvinyl alcohol,polyvinyl chloride, heterocyclic polymers, polyesters, modifiedpolyolefins, polysilanes, polysiloxane (silicone) polymers, andcopolymers and mixtures thereof.
 33. The structure of claim 20 whereinthe first material and the second material are optical materials andwherein the two materials differ in values of index-of-refractionbetween each other by at least about 0.005 at infrared, visible orultraviolet wavelengths.
 34. The structure of claim 20 wherein the firstmaterial and the second material are optical materials and wherein thetwo materials differ in values of index-of-refraction between each otherby at least about 0.1 at infrared, visible or ultraviolet wavelengths.35. The structure of claim 20 wherein the polymer-inorganic particleblend has a non-linear optical response at infrared, visible orultraviolet wavelengths.
 36. The structure of claim 20 wherein theparticle-inorganic particle blend comprises a polymer-inorganic particlemixture.
 37. The structure of claim 20 wherein the particle-inorganicparticle blend comprises a polymer-inorganic particle composite.
 38. Thestructure of claim 20 wherein the second material comprises apolymer-inorganic particle blend.
 39. The structure of claim 20 whereinthe first material comprises at least about 10 weight percent inorganicparticles.
 40. The structure of claim 20 wherein the inorganic particlescomprise a metal oxide or a metal nitride.
 41. The structure of claim 20wherein the dopant comprises Ho, Eu, Ce, Tb, Dy, Er, Yb, Nd, La, Y, Pr,Tm, Bi, Sb, Zr, Pb, Li, Na, K, Ba, B, Ge, W, Ca, Cr, Ga, Al, Mg, Sr, Zn,Ti, Ta, Nb, Mo, Th, Cd, Sn or combinations thereof.
 42. The structure ofclaim 20 wherein essentially no inorganic particles have a particlediameter greater than about four times the average particle diameter.43. The structure of claim 20 wherein the inorganic particles have adistribution of diameters with at least about 95 percent of the primaryparticles having a diameter greater than about 60 percent of the averagediameter and less than about 140 percent of the average diameter. 44.The structure of claim 20 wherein the polymer inorganic-particle blendcomprises a polymer selected from the group consisting of polyamides(nylons), polyimides, polycarbonates, polyurethanes, polyacrylonitrile,polyacrylic acid, polyacrylates, polyacrylamides, polyvinyl alcohol,polyvinyl chloride, heterocyclic polymers, polyesters, modifiedpolyolefins, polysilanes, polysiloxane (silicone) polymers, andcopolymers and mixtures thereof.
 45. The structure of claim 1 whereinessentially no inorganic particles have a particle diameter greater thanabout four times the average particle diameter.
 46. The structure ofclaim 1 wherein the inorganic particles have a distribution of diameterswith at least about 95 percent of the primary particles having adiameter greater than about 60 percent of the average diameter and lessthan about 140 percent of the average diameter.
 47. The structure ofclaim 1 wherein the inorganic particles have an average particlediameter of no more than about 100 nm.
 48. The optical structure ofclaim 1 wherein the inorganic particles comprise a metal nitride orsilicon nitride.
 49. The structure of claim 4 wherein essentially noinorganic particles have a particle diameter greater than about fourtimes the average particle diameter.
 50. The structure of claim 4wherein the inorganic particles have a distribution of diameters with atleast about 95 percent of the primary particles having a diametergreater than about 60 percent of the average diameter and less thanabout 140 percent of the average diameter.
 51. The optical structure ofclaim 4 wherein the inorganic particles comprise a metal nitride orsilicon nitride.